<PAGE>
 
                                                                    Exhibit 10.5
                    DATE OF LEASE EXECUTION:  May 21, 1996


                                   ARTICLE 1

                                REFERENCE DATA

1.1 SUBJECTS REFERRED TO:

    Each reference in this Lease to any of the following subjects shall be
construed to incorporate the data stated for that subject in this Section 1.1:

LANDLORD:  The Trustees of Lexington Development Company Trust

MANAGING AGENT:  Spaulding and Slye Services Limited Partnership

LANDLORD'S & MANAGING AGENT'S ADDRESS:

     c/o Spaulding and Slye Company
     25 Mall Road
     Burlington, MA  01803
     Attn:  Treasurer

LANDLORD'S REPRESENTATIVE:  Mr. Bruce Nolen

TENANT:  Linkage, Inc., a Massachusetts corporation

TENANT'S ADDRESS (FOR NOTICE AND BILLING):    One Forbes Road,
                                              Lexington, MA  02173

TENANT'S REPRESENTATIVE:  Mr. Larry Carr, Senior Vice President

BUILDING ADDRESS:  One Forbes Road, Lexington, MA

RENTABLE FLOOR AREA
OF TENANT'S SPACE:       14,404 square feet as of the Commencement Date; 21,279
                         as of the First Expansion Commencement Date; and 24,530
                         as of the Second Expansion Commencement Date

TOTAL RENTABLE FLOOR AREA OF THE BUILDING:  24,530 square feet

SCHEDULED TERM COMMENCEMENT DATE:  September 1, 1996

                                      -1-
<PAGE>
 
SCHEDULED FIRST EXPANSION COMMENCEMENT DATE:  March 1, 1997

SCHEDULED SECOND EXPANSION COMMENCEMENT DATE:  August 1, 1997

TERM EXPIRATION DATE:  December 31, 2002

APPROXIMATE TERM:   76 months subject to earlier termination in accordance with
                    the provisions hereof

ANNUAL BASE RENT COMMENCEMENT DATE:       Three (3) months after the
                                          Commencement Date

ANNUAL BASE RENT RATE:   $16.00 (p.r.s.f.) in 1996 and 1997;
                         $17.00 (p.r.s.f.) in 1998 through 2001; and
                         $18.00 (p.r.s.f.) in 2002

ANNUAL BASE RENT:   (a) $230,464 for the period from the Annual Base Rent
                    Commencement Date through the First Expansion Commencement
                    Date (based on 14,404 r.s.f. x $16.00);

                    (b) $340,464 for the period from the First Expansion
                    Commencement Date through the Second Expansion Commencement
                    Date (based on 21,279 r.s.f. x $16.00);

                    (c) $392,480 for the period from the Second Expansion
                    Commencement Date through December 31, 1997 (based on 24,530
                    r.s.f. x $16.00)

                    (d) $417,010 for the period from January 1, 1998 through
                    December 31, 2001 (based on 24,530 r.s.f. x $17.00); and

                    (e) $441,540 for the period from January 1, 2002 through
                    December 31, 2002 (based on 24,530 r.s.f. x $18.00)

ANNUAL ESTIMATED ELECTRICAL COST:  $0.85 (p.r.s.f.)

ANNUAL ESTIMATED ELECTRICAL COST TO TENANT'S SPACE
(Incl. in Annual Rent):

     (a) $12,243.40 as of the Commencement Date

     (b) $18,087.50 as of the First Expansion Commencement Date

     (c) $20,850.50 as of the Second Expansion Commencement Date

                                      -2-
<PAGE>
 
ANNUAL RENT (equal to the sum of Annual Base Rent and Annual Estimated
Electrical Cost to Tenant's Space):

     (a)  $12,243.40 for the period from the Commencement Date through the
     Annual Base Rent Commencement Date;

     (b)  $242,707.40 for the period from the Annual Base Rent Commencement Date
     through the First Expansion Commencement Date;

     (c)  $358,551.50 for the period from the First Expansion Commencement Date
     through the Second Expansion Commencement Date;

     (d)  $413,330.50 for the period from the Second Expansion Commencement Date
     through December 31, 1997;

     (e)  $437,850.50 for the period from January 1, 1998 through December 31,
     2001; and

     (f)  $462,390.50 for the period from January 1, 2002, through December 31,
     2002.

ANNUAL ESTIMATED OPERATING COSTS:   $165,577.50; $6.75 (p.r.s.f.)

SECURITY DEPOSIT:   $50,000, subject to the provisions of Article XI hereof

TENANT ALLOWANCE:        $13.50 (p.r.s.f.), as allocated pursuant to Article III
                         hereof

PERMITTED USES:     Office uses and uses accessory thereto permitted under
                    applicable zoning and other legal requirements

PUBLIC LIABILITY INSURANCE:   BODILY INJURY: $2,000,000
                              PROPERTY DAMAGE: $1,000,000

OPTION TO EXTEND:   One option to extend for a period of three years for the
                    period from January 1, 2003 to December 31, 2005.

1.2 EXHIBITS.

     The exhibits listed below in this section are incorporated in this Lease by
reference and are to be construed as part of this Lease:

     EXHIBIT A-1    Plan showing Tenant's Space as of the Commencement Date.

                                      -3-
<PAGE>
 
     EXHIBIT A-2    Plan showing Tenant's Space as of the First Expansion
                    Commencement Date.

     EXHIBIT A-3    Plan showing Tenant's Space as of the Second Expansion
                    Commencement Date.

     EXHIBIT B      Landlord's Services.

     EXHIBIT C      Rules and Regulations.


1.3  TABLE OF CONTENTS                                            PAGE
<TABLE>
<S>                                                               <C>
ARTICLE I - REFERENCE DATA.........................................  1
      1.1   SUBJECTS REFERRED TO...................................  1
      1.2   EXHIBITS...............................................  3

ARTICLE II - PREMISES AND TERM.....................................  7
      2.1   PREMISES...............................................  7
      2.2   TERM...................................................  7
      2.3   OPTION TO EXTEND.......................................  8

ARTICLE III - CONSTRUCTION.........................................  9
      3.1   INITIAL CONSTRUCTION...................................  9
      3.2   PREPARATION OF PREMISES FOR OCCUPANCY.................. 11
      3.3   GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.......... 13
      3.4   REPRESENTATIVES........................................ 13
      3.5   SIGNAGE................................................ 13
      3.6   IMPROVEMENTS TO BUILDING LOBBY......................... 14

ARTICLE IV - RENT.................................................. 14
      4.1   RENT................................................... 14
      4.2   OPERATING COSTS; ESCALATION............................ 14
      4.3   ESTIMATED ESCALATION PAYMENTS.......................... 16
      4.4   ELECTRICITY............................................ 17
      4.5   CHANGE OF FISCAL YEAR.................................. 17
      4.6   PAYMENTS............................................... 17

ARTICLE V - LANDLORD' S COVENANTS.................................. 18
      5.1   LANDLORD' S COVENANTS DURING THE TERM.................. 18
      5.2   INTERRUPTIONS.......................................... 18

ARTICLE VI - TENANT' S COVENANTS................................... 19
</TABLE>
                                      -4-
<PAGE>
 
<TABLE>
<S>                                                                     <C>
      6.1   TENANT' S COVENANTS DURING THE TERM......................... 19

ARTICLE VII - CASUALTY AND TAKING....................................... 24
      7.1   CASUALTY AND TAKING......................................... 24
      7.2   RESERVATION OF AWARD........................................ 25

ARTICLE VIII - RIGHTS OF MORTGAGEE...................................... 25
      8.1   PRIORITY OF LEASE........................................... 25
      8.2   RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S
            LIABILITY................................................... 26
      8.3   MORTGAGEE'S ELECTION........................................ 26
      8.4   NO PREPAYMENT OR MODIFICATION, ETC.......................... 27
      8.5   NO RELEASE OR TERMINATION................................... 27
      8.6   CONTINUING OFFER............................................ 27
      8.7   MORTGAGEE'S APPROVAL........................................ 28

ARTICLE IX - DEFAULT.................................................... 28
      9.1   EVENTS OF DEFAULT........................................... 28
      9.2   TENANT'S OBLIGATIONS AFTER TERMINATION...................... 29

ARTICLE X - MISCELLANEOUS............................................... 30
      10.1  NOTICE OF LEASE............................................. 30
      10.2  INTENTIONALLY DELETED....................................... 30
      10.3  NOTICES FROM ONE PARTY TO THE OTHER......................... 30
      10.4  BIND AND INURE.............................................. 31
      10.5  NO SURRENDER................................................ 31
      10.6  NO WAIVER, ETC.............................................. 31
      10.7  NO ACCORD AND SATISFACTION.................................. 32
      10.8  CUMULATIVE REMEDIES......................................... 32
      10.9  LANDLORD'S RIGHT TO CURE.................................... 32
      10.10 ESTOPPEL CERTIFICATE........................................ 32
      10.11 WAIVER OF SUBROGATION....................................... 33
      10.12 ACTS OF GOD................................................. 33
      10.13 BROKERAGE................................................... 33
      10.14 SUBMISSION NOT AN OFFER..................................... 33
      10.15 APPLICABLE LAW AND CONSTRUCTION............................. 34

ARTICLE XI - SECURITY DEPOSIT........................................... 34
</TABLE>

                                      -5-
<PAGE>
 
                                  ARTICLE II

                               PREMISES AND TERM

2.1 PREMISES.

     Subject to and with the benefit of the provisions of this Lease relating to
the parcel on which the Building is located (the "Lot"), Landlord hereby leases
to Tenant, and Tenant leases from Landlord, effective on the Commencement Date
(as defined in Section 2.2 hereof), Tenant's Space in the Building as shown on
Exhibit A-1 (the "Initial Premises"); effective on the First Expansion
Commencement Date (as defined in Section 3.2 hereof), Tenant's Space in the
Building as shown on Exhibit A-2 (the "Interim Premises"); and effective on the
Second Expansion Commencement Date (as defined in Section 3.2 hereof), Tenant's
Space in the Building as shown on Exhibit A-3 (the "Final Premises"), in each
case excluding exterior faces of exterior walls, the common facilities area and
building service fixtures and equipment serving exclusively or in common other
parts of the Building.  Tenant's Space, with such exclusions, is hereinafter
referred to as the "Premises," consisting of the Initial Premises as of the
Commencement Date; the Interim Premises as of the First Expansion Commencement
Date; and the Final Premises as of the Second Expansion Commencement Date.  (The
portion of the Interim Premises not included in the Initial Premises is
hereinafter referred to as the "First Expansion Premises," and the portion of
the Final Premises not included in the Interim Premises is hereinafter referred
to as the "Second Expansion Premises".)

     Tenant shall have, as appurtenant to the Premises, the right to use in
common with others entitled thereto: (a) the common facilities included in the
Building or on the Lot, including the parking facility, if any, on a first-come,
first-served basis, to the extent and in the location from time to time
designated by Landlord, and (b) the building service fixtures and equipment
serving the Premises.

     Landlord reserves the right from time to time, without unreasonable
interference with Tenant's use, (a) to install, repair, replace, use, maintain
and relocate for service to the Premises and to other parts of the Building or
either, building service fixtures and equipment wherever located in the Building
and (b) to alter or relocate any common facilities, it being understood that
parking spaces may be relocated on or off the Lot from time to time by Landlord,
provided that in all events substitutions are substantially equivalent.

2.2 TERM.

     To have and to hold for a period (the "Term") commencing on the earliest of
(a) the date on which the Premises are deemed ready for occupancy as provided in
Section 3.2, and (b) the date on which Tenant occupies all or any part of the
Premises 

                                      -6-
<PAGE>
 
(whichever of said dates is appropriate being hereafter referred to as the
"Commencement Date"), and continuing until the Term Expiration Date, unless
sooner terminated as provided in Section 3.2 or 7.1 or in Article IX. Landlord
and Tenant will execute, upon request of either, a certificate acknowledging the
Commencement Date of this Lease once such commencement date has occurred.

2.3 OPTION TO EXTEND.

     Tenant shall have the right and option to extend the Term for one
additional period of three (3) years (the "Extension Term") commencing upon the
expiration of the original Term referred to in Section 1.1 of the Lease (the
"Original Term"), provided that (i) Tenant shall give Landlord notice of
Tenant's exercise of such option at least seven (7) months prior to the
expiration of the Original Term; (ii) Tenant shall not be in default at either
the time of giving such notice or at the time of the commencement of the
Extension Term in the performance or observance of any of the terms and
provisions of this Lease on the part of the Tenant to be performed or observed;
(iii) the Lease remains in full force and effect; and (iv) Tenant has neither
assigned the Lease nor sublet the Premises or any portion thereof.  Prior to the
exercise by Tenant of such option, the expression "Term" shall mean the Original
Term, and after the exercise by Tenant of such option, the expression "Term"
shall mean the Original Term as it has been extended by the Extension Term.
Except as expressly otherwise provided in the following paragraph, all the
terms, covenants, conditions, provisions and agreements in the Lease contained
shall be applicable to the Extension Term, except Tenant's Extension Option set
forth in this Section 2.3 which shall not be applicable to the Extension Term.
If Tenant shall give notice of its exercise of said option to extend in the
manner and within the time period provided aforesaid, the Term shall be extended
upon the giving of such notice without the requirement of any further action on
the part of either Landlord or Tenant; provided, however, that upon the written
request of either party, the parties shall execute an amendment to the Lease
confirming the extension of the Lease effected hereby.  If Tenant shall fail to
give timely notice of the exercise of any such option as aforesaid, Tenant shall
have no right to extend the Term of this Lease, time being of the essence of the
foregoing provisions.

     The Annual Base Rent payable during the Extension Term shall be the amount
being the Fair Market Rent for the Premises, as determined below, as of the
commencement of the Extension Term. If for any reason the Annual Base Rent
payable during the Extension Term has not been determined as of the commencement
of the Extension Term, Tenant shall pay Annual Base Rent payable during the last
year of the Original Term until the Annual Base Rent for the Extension Term is
determined, at which time an appropriate adjustment, if any, shall be made.  For
purposes hereof, the Fair Market Rent shall mean the fair rent for the Premises
as of the commencement of the Extension Term under market conditions 

                                      -7-
<PAGE>
 
then existing without allowance for tenant improvements as reasonably determined
by Landlord.


                                  ARTICLE III

                                 CONSTRUCTION

3.1 INITIAL CONSTRUCTION.

     Landlord shall improve the Initial Premises in accordance with plans and
specifications there for to be mutually agreed upon by Landlord and Tenant (the
"Initial Leasehold Improvements") no later than June 1, 1996, Landlord and
Tenant agreeing to act diligently and in good faith to agree upon such plans and
specifications.  The First Expansion Premises and the Second Expansion Premises
shall be improved by Landlord in accordance with construction drawings and
specifications approved by Landlord and Tenant in accordance with the following
provisions.

     On or before December 1, 1996 with respect to the First Expansion Premises
and on or before May 1, 1997 with respect to the Second Expansion Premises,
Tenant shall provide to Landlord for approval complete sets of construction
drawings and specifications (the "Complete Plans") by Landlord's architect or an
architect approved by Landlord and Landlord's engineer, including but not
limited to:

     a.   Furniture and Equipment Layout Plans
     b.   Dimensioned Partition Plans
     c.   Dimensioned Electrical and Telephone Outlet Plans
     d.   Reflected Ceiling Plans
     e.   Door and Hardware Schedules
     f.   Room Finish Schedules including wall, carpet and floor tile colors
     g.   Electrical, mechanical and structural engineering plans
     h.   All necessary construction details and specifications.

Landlord and Tenant shall initial the Complete Plans after the same have been
submitted by Tenant and approved by Landlord.

     All of Tenant's construction, installation of furnishings, and later
changes or additions shall be coordinated with any work being performed by
Landlord in such manner as to maintain harmonious labor relations and not to
damage the Building or Lot or interfere with Building operations.  Except for
installation of furnishings and the installation of telephone outlets which must
be performed by the local telephone company at Tenant's direction and expense,
all work described in the Initial Leasehold Improvements, all work described in
the Complete Plans for the First 

                                      -8-
<PAGE>
 
Expansion Premises (the First Expansion Leasehold Improvements"), and all work
described in the Complete Plans for the Second Expansion Premises (the "Second
Expansion Leasehold Improvements") (collectively with the Initial Leasehold -
Improvements and the First Expansion Leasehold Improvements, the "Leasehold
Improvements") shall be performed by Landlord's general contractor, Spaulding
and Slye Construction Company.

     Tenant shall pay to Landlord as additional rent a sum equal to all costs
incurred by Landlord on account of the Leasehold Improvements (excluding,
however, the Tenant Allowance which shall apply separately to the Initial
Leasehold Improvements, the First Expansion Leasehold Improvements and the
Second Expansion Leasehold Improvements, and with respect to the Initial
Leasehold Improvements only, an additional $2,000 allowance for further
improvements to the conference room and training area, but including in the
costs so incurred the cost to Landlord of Landlord's Contractor's overhead and
profit equal to 15% of costs of work and all architectural and engineering costs
incurred by Landlord), hereinafter called "Tenant Improvement Reimbursement to
Landlord" or "TIR."  Any portion of the Tenant Allowance unused in connection
with the Initial Leasehold Improvements may be used in connection with the First
Expansion Leasehold Improvements and the Second Expansion Leasehold
Improvements; and any portion of the remaining Tenant Allowance unused in
connection with the Initial Leasehold Improvements and the First Expansion
Leasehold Improvements may be used in connection with the Second Expansion
Leasehold Improvements; provided, however, that Tenant must use a portion of the
Tenant Allowance with respect to each of the Initial Leasehold Improvements and
the First Leasehold Improvements to construct, at a minimum, building standard
carpet, building standard paint, and building standard ceiling.  No portion of
the Tenant Allowance unused in connection with the Initial Leasehold
Improvements, the First Expansion Leasehold Improvements and the Second
Expansion Leasehold Improvements may be used in connection with any other
improvements for any other space in the Building and shall be forfeited.

     Tenant shall pay to Landlord fifty percent (50%) of the TIR, if any,
applicable to each of the Initial Leasehold Improvements, the First Expansion
Leasehold Improvements and the Second Expansion Leasehold Improvements prior to
Landlord's commencement of construction of each of the Initial Leasehold
Improvements, the First Expansion Leasehold Improvements, and the Second
Expansion Leasehold Improvements, respectively.  Thereafter, in the case of each
of the Initial Leasehold Improvements, the First Expansion Leasehold
Improvements and the Second Expansion Leasehold Improvements, Tenant shall pay
TIR to Landlord as construction of the applicable Leasehold Improvements
progresses, on submission by Landlord to Tenant of a statement on or about the
first day of each month showing construction and design costs incurred.  Such
statement shall be accompanied by a certificate of Landlord's Contractor that
all payments then due to laborers, materialmen and subcontractors have been
made, less the aggregate amount 

                                      -9-
<PAGE>
 
of prior monthly progress payments made by Tenant. On the earlier of occupancy
or the applicable Commencement Date, Tenant shall pay to Landlord a sum equal to
the unpaid balance of TIR, if any, applicable to the then Leasehold
Improvements. In addition to paying TIR as above provided, Tenant shall pay an
amount equal to all costs incurred by Landlord as a result of any change orders
signed by Tenant and Landlord affecting the plans and specifications set forth
in Exhibit B or the Complete Plans for either the First Expansion Premises or
the Second Expansion Premises, including the cost to Landlord of Landlord's
Contractor's overhead and profit equal to 15% of those costs exclusive of
overhead and profit. Amounts due and payable on account of such change orders
shall be included in the monthly statements relating to TIR provided for above,
and Tenant shall pay therefor in accordance with each such statement within
thirty (30) days, and in all events by the applicable Commencement Date.

     Subject to Section 6.1.15, Landlord will not approve any construction,
alterations, or additions requiring unusual expense to readapt the Premises to
normal office use on lease termination or increasing the cost of construction,
insurance or taxes on the Building or of Landlord's services called for by
Section 5.1 unless Tenant first gives assurances acceptable to Landlord that
such readaptation will be made prior to such termination without expense to
Landlord and makes provisions acceptable to Landlord for payment of such
increased cost.  Landlord will also disapprove any alterations or additions
requested by Tenant which will delay completion of the Premises or the Building.
All changes and additions shall be part of the Building except such items as by
writing at the time of approval the parties agree either shall be removed by
Tenant on termination of this Lease, or shall be removed or left at Tenant's
election.

3.2 PREPARATION OF PREMISES FOR OCCUPANCY.

     Landlord agrees to use reasonable efforts to have ready for occupancy (a)
the Initial Premises on or before the Scheduled Term Commencement Date, (b) the
First Expansion Premises on or before the First Expansion Commencement Date and
(c) the Second Expansion Premises on or before the Second Expansion Commencement
Date, each of which shall, however, be extended for a period equal to that of
any delays due to governmental regulations, unusual scarcity of or inability to
obtain labor or materials, labor difficulties, casualty or other causes beyond
Landlord's reasonable control. Each of the Initial Premises, the First Expansion
Premises and the Second Expansion Premises shall be deemed ready for occupancy
on the date on which the applicable Leasehold Improvements, as mutually agreed
upon by Landlord and Tenant pursuant to Section 3.1 hereof with respect to the
Initial Leasehold Improvements and as specified in the Complete Plans with
respect to the First Expansion Premises or the Second Expansion Premises, as
applicable, are ready for occupancy as evidenced by a certificate of occupancy
therefor, it being understood that so-called punchlist items which can be fully
completed without material 

                                      -10-
<PAGE>
 
interference with Tenant and other items which because of the season or weather
or the nature of the item are not practicable to do at the time may not have
been completed, provided that none of said items is necessary to make such
portion of the Premises tenantable for the Permitted Uses and provided further
that all said items shall be completed within thirty (30) days after occupancy,
subject to delay for causes beyond Landlord's reasonable control; provided,
however, that if Landlord is unable to complete construction due to delay in
Tenant's compliance with the provisions of Section 3.1 of this Lease, then such
portion of Premises shall be deemed ready for occupancy no later than the
Scheduled Term Commencement Date in the case of the Initial Premises, the First
Expansion Commencement Date in the case of the First Expansion Premises, and the
Second Expansion Commencement Date in the case of the Second Expansion Premises.
Tenant and Landlord or Landlord's architect shall inspect the Initial Premises,
the First Expansion Premises or the Second Expansion Premises, as the case may
be, to determine the punchlist items, if any, which must be completed by
Landlord after the applicable Commencement Date. Window blinds in the Premises
will be delivered in a clean and operable condition.

     Subject to applicable legal requirements, Landlord shall permit Tenant
access for installing equipment and furnishings in the Initial Premises prior to
the Term if it can be done without material interference with completion of the
Building or remaining portions of the Initial Leasehold Improvements, and shall
also permit Tenant such access in the First Expansion Premises and the Second
Expansion Premises prior to the applicable Expansion Commencement Date if it can
be done without material interference with completion of the Building or
remaining portions of the applicable Expansion Leasehold Improvements.

     In the event of Tenant's failure to comply with the provisions of Section
3.1 to submit information or to deliver construction drawings and specifications
which meet Landlord's approval, Landlord may, at Landlord's option, exercisable
by notice to Tenant, either (a) terminate this Lease on the date specified in
said notice to Tenant (i) with respect to the entire Premises in the case of
such failure at any time, (ii) with respect to the First and Second Expansion
Premises, but not the Initial Premises, in the case of such failure in
connection with the First Expansion Premises, or (iii) with respect to the
Second Expansion Premises, but not the Initial Premises or the First Expansion
Premises, in the case of such failure in connection with the Second Expansion
Premises, and upon any such termination Landlord shall have all the rights
provided in Article IX of this Lease in the event of Tenant's default, or (b)
assess Tenant liquidated damages in an amount equal to the Annual Rent relating
to the portion of the Premises to which such failure relates divided by 365 for
each day such failure continues, which damages shall be paid to Landlord on the
Commencement Date.

                                      -11-
<PAGE>
 
3.3 GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.

     All construction work required or permitted by this Lease, whether by
Landlord or by Tenant, shall be done in a good and workmanlike manner and in
compliance with all applicable laws and all lawful ordinances, regulations and
orders of governmental authority and insurers of the Building.  Either party may
inspect the work of the other at reasonable times and promptly shall give notice
of observed defects.  Landlord's obligations under Section 3.1 shall be deemed
to have been performed (a) with respect to the Initial Premises, when Tenant
commences to occupy any portion of the Initial Premises for the Permitted Uses,
(b) with respect to the First Expansion Premises, when Tenant commences to
occupy any portion of the First Expansion Premises for the Permitted Uses, and
(c) with respect to the Second Expansion Premises, when Tenant commences to
occupy any portion of the Second Expansion Premises for the Permitted Uses, in
each case, however, with the exception of items which are incomplete or do not
conform with the requirements of Section 3.1 and as to which Tenant shall in
either case have given written notice to Landlord prior to such commencement.
If Tenant shall not have commenced to occupy the Initial Premises, the First
Expansion Premises or the Second Expansion Premises, as the case may be, for the
Permitted Uses within 30 days after they are deemed ready for occupancy as
provided in Section 3.2, a certificate of completion by a licensed architect or
registered engineer shall be conclusive evidence that Landlord has performed all
such obligations except for items stated in such certificate to be incomplete or
not in conformity with such requirements.

3.4 REPRESENTATIVES.

     Each party authorizes the other to rely in connection with their respective
rights and obligations under this Article III upon approval and other actions on
the party's behalf by Landlord's Representative in the case of Landlord or
Tenant's Representative in the case of Tenant or by any person designated in
substitution or addition by notice to the party relying.

3.5 SIGNAGE.

     Subject to Landlord's prior approval, Landlord will install on behalf of
Tenant signage conforming to Building Standards identifying Tenant at the
entrance to the Premises, on the tenant directory in the lobby serving the
Building, and on the exterior sign located at the intersection of Forbes Road
and Route 2A.  Subject to Landlord's prior approval as to design and location,
Landlord will also install, at Tenant's sole cost, an exterior monument sign
visible from Forbes Road identifying Tenant.  All signage must comply with all
local ordinances and design criteria and other applicable legal requirements.

                                      -12-
<PAGE>
 
3.6 IMPROVEMENTS TO BUILDING LOBBY.

     Landlord will recarpet and repaint the lobby to the Building and install
new lighting therein.  Landlord shall consult with Tenant in selecting paint
colors, carpeting and lighting fixtures for the lobby before making a final
decision on such items. However, Landlord's decision shall be final.  Landlord
agrees to (i) commence the lobby improvements within thirty (30) days after the
Commencement Date, and (ii) complete such improvements within forty-five (45)
days after the Commencement Date, in each case, subject to delays caused by
Tenant and other causes beyond Landlord's reasonable control.


                                  ARTICLE IV

                                     RENT

4.1 RENT.

     Tenant agrees to pay rent to Landlord without any offset or reduction
whatever (except as made in accordance with the express provisions of this
Lease), equal to 1/12th of the Annual Base Rent in equal installments in advance
on the first day of each calendar month included in the Term; and for any
portion of a calendar month at the beginning or end of the Term, at the
proportionate rate payable for such portion, in advance.

4.2 OPERATING COSTS; ESCALATION.

     Tenant's proportionate share of the Annual Estimated Operating Costs shall
be determined by multiplying Annual Estimated Operating Costs by a fraction, the
numerator of which is the Rentable Floor Area of Tenant's Space, and the
denominator of which is the Total Rentable Floor Area of the Building.

     Tenant shall pay to Landlord, as additional rent, Operating Cost Escalation
(as defined below), if any, on or before the thirtieth day following receipt by
Tenant of Landlord's Statement (as defined below).  As soon as practicable after
the end of each Fiscal Year ending during the Term and after Lease termination,
Landlord shall render a statement ("Landlord's Statement") in reasonable detail
and according to usual accounting practices certified by Landlord and showing
for the preceding Fiscal Year or fraction thereof, as the case may be,
Landlord's Operating Costs,

     excluding the interest and amortization on mortgages for the Building and
Lot or leasehold interests therein and the cost of special services rendered to
tenants (including Tenant) for which a special charge is made,

                                      -13-
<PAGE>
 
     but including, without limitation:  real estate taxes on the Building and
Lot; installments and interest on assessments for public betterments or public
improvements; expenses of any proceedings for abatement of taxes and assessments
with respect to any fiscal year or fraction of a fiscal year; premiums for
insurance; fees payable to third parties for financial audits of Landlord's
Operating Costs; compensation and all fringe benefits, worker's compensation
insurance premiums and payroll taxes paid by Landlord to, for or with respect to
all persons engaged in the operating, maintaining, or cleaning of the Building
and Lot; all utility charges not billed directly to tenants by Landlord or the
utility; payments to independent contractors under service contracts for
cleaning, operating, managing, maintaining and repairing the Building and Lot
(which payments may be to affiliates of Landlord provided the same are at
reasonable rates consistent with the type of occupancy and the managing agent
space for a building office on the ground floor or above; if the Building shares
common areas or facilities with another building or buildings, the Building's
pro rata share (as reasonably determined by Landlord) of the cost of cleaning,
operating, managing (including the cost of the management office for such
buildings and facilities), maintaining and repairing such common areas and
facilities; and all other reasonable and necessary expenses paid in connection
with the cleaning, operating, managing, maintaining and repairing of the
Building and Lot, or either, and properly chargeable against income, it being
agreed that if Landlord installs a new or replacement capital item for the
purpose of reducing Landlord's Operating Costs during the Term of the Lease, the
cost thereof as reasonably amortized by Landlord in accordance with generally
accepted accounting practices, with interest at the average prime commercial
rate in effect from time to time at the three largest national banks in Boston,
Massachusetts on the unamortized amount, shall be included in Landlord's
Operating Costs.  Landlord's Statement shall also show the average number of
square feet of the Building which were occupied for the preceding fiscal year of
fraction thereof.

     "Operating Cost Escalation" shall be equal to the difference, if any,
between:

     (a) the product of Landlord's Operating Costs as indicated in Landlord's
Statement and a fraction, the numerator of which shall be the Rentable Floor
Area of Tenant's Space (adjusted to reflect the First Expansion Commencement
Date and the Second Expansion Commencement Date, where applicable) and the
denominator of which shall be one-half of the Total Rentable Floor Area of the
Building plus one-half of the average number of such square feet as are occupied
during such fiscal year or fraction thereof, and

     (b) the product of the Annual Estimated Operating Costs (as reduced
pursuant to this Section 4.2 and Section 4.4) and a fraction, the numerator of
which shall be the Rentable Floor Area of Tenant's Space and the denominator of
which shall be the Total Rentable Floor Area of the Building.

                                      -14-
<PAGE>
 
     If the management fee is reduced by reason of a tenant's default in the
payment of Annual Rent or additional rent, Landlord shall reduce the Annual
Estimated Operating Costs by the amount of such reduction in the management fee.
In case of special services which are not rendered to all areas of a comparable
basis, the proportion allocable to the Premises shall be the same proportion
which the Rentable Floor Area of Tenant's Space bears to the total rentable
floor area to which such service is so rendered (such latter area to be
determined in the same manner as the Total Rentable Floor Area of the Building).

     The term "real estate taxes" as used above shall mean all taxes of every
kind and nature assessed by any governmental authority on the Lot, the Building
and improvements, or both, which the Landlord shall become obligated to pay
because of or in connection with the ownership, leasing and operation of the
Lot, the Building and improvements, or both, subject to the following: There
shall be excluded from such taxes all income taxes, excess profits taxes, excise
taxes, franchise taxes, and estate, succession, inheritance and transfer taxes,
provided, however, that if at any time during the Term the present system of ad
valorem taxation of real property shall be changed so that in lieu of the whole
or any part of the ad valorem tax on real property, there shall be assessed on
Landlord a capital levy or other tax on the gross rents received with respect to
the Lot, Building and improvements, or both, or a federal, state, county,
municipal, or other local income, franchise, excise or similar tax, assessment,
levy or charge (distinct from any now in effect) measured by or based, in whole
or in part, upon any such gross rents, then any and all of such taxes,
assessments, levies or charges, to the extent so measured or based, shall be
deemed to be included within the term "real estate taxes."

     Notwithstanding any other provision of this Section 4.2, if the Term
expires or is terminated as of a date other than the last day of a fiscal year,
then for such fraction of a fiscal year at the end of the Term, Tenant's last
payment to Landlord under this Section 4.2 shall be made on the basis of
Landlord's best and reasonable estimate of the items otherwise includable in
Landlord's Statement and shall be made on or before the later of (a) 10 days
after Landlord delivers such estimate to Tenant or (b) the last day of the Term,
with an appropriate payment or refund to be made upon submission of Landlord's
Statement.

4.3 ESTIMATED ESCALATION PAYMENTS.

     If, with respect to any fiscal year or fraction thereof during the Term,
Landlord estimates that Tenant shall be obligated to pay Operating Cost
Escalation, then Tenant shall pay, as additional rent, on the first day of each
month of such fiscal year and each ensuing fiscal year thereafter, Estimated
Monthly Escalation Payments equal to 1/12th of the estimated Operating Cost
Escalation for the respective fiscal year, with an appropriate additional
payment or refund to be made within 30 days after Landlord's Statement is
delivered to Tenant.  Landlord may adjust such Estimated 

                                      -15-
<PAGE>
 
Monthly Escalation Payment from time to time and at any time during a fiscal
year, and Tenant shall pay, as additional rent, on the first day of each month
following receipt of Landlord's notice thereof, the adjusted Estimated Monthly
Escalation Payment.

4.4 ELECTRICITY.

     Tenant shall be responsible for paying its pro rata share of all
electricity charges relating to its use of the Premises as reasonably determined
by Landlord. Accordingly, the Annual Rent may be adjusted to reflect increases
in the Estimated Cost of Electrical Service to Tenant's Space.  At Tenant's
option, if Tenant is in occupancy of the Total Rentable Floor Area of the
Building, Tenant may pay all electricity charges directly to the utility
providing electric service, provided that all payments are made prior to the
date that such charges are due.  In the event that Tenant exercises such option,
Tenant shall no longer pay the Estimated Electrical Service to Tenant's Space or
other electrical costs to Landlord and the Annual Estimated Operating Costs
shall be reduced to reflect the decrease in Landlord's Operating Costs resulting
therefrom.  Annual Base Rent shall not be adjusted.

4.5 CHANGE OF FISCAL YEAR.

     Landlord shall have the right from time to time to change the periods of
accounting under Section 4.2 to any annual period other than a fiscal year, and
upon any such change all items referred to in this Section 4.4 shall be
appropriately apportioned.  In all Landlord's Statements rendered under this
Section 4.4, amounts for periods partially within and partially without the
accounting periods shall be appropriately apportioned, and any items which are
not determinable at the time of a Landlord's Statement shall be included therein
on the basis of Landlord's estimate, and with respect thereto Landlord shall
render promptly after determination a supplemental Landlord's Statement, and
appropriate adjustment shall be made according thereto.  All Landlord's
Statements shall be prepared on an accrual basis of accounting and in accordance
with generally acceptable accounting practices.

4.6 PAYMENTS.

     All payments of Annual Rent and additional rent shall be made to Managing
Agent, or to such other person as Landlord may from time to time designate.  If
any installment of Annual Rent or additional rent or on account of leasehold
improvements is paid more than 5 days after the due date thereof, at Landlord's
election, it shall bear interest at a rate equal to the average prime commercial
rate from time to time established by the three largest national banks in
Boston, Massachusetts plus 2% per annum from such due date, which interest shall
be immediately due and payable as further additional rent.

                                      -16-
<PAGE>
 
                                   ARTICLE V
                             LANDLORD' S COVENANTS


5.1 LANDLORD' S COVENANTS DURING THE TERM.

     Landlord covenants during the Term:

     5.1.1  Building Services - To furnish, through Landlord's employees or
independent contractors, the services listed in Exhibit B;

     5.1.2  Additional Building Services - To furnish, through Landlord's
employees or independent contractors, reasonable additional Building operation
services upon reasonable advance request of Tenant at equitable rates from time
to time established by Landlord to be paid by Tenant, it being understood that
HVAC services for periods other than Monday through Friday from 8:00 a.m. to
6:00 p.m. and Saturday from 8:00 a.m. to 1:00 p.m. are additional building
services;

     5.1.3  Repairs - Except as otherwise provided in Article VII, to make such
repairs to the roof, exterior walls, floor slabs, other structural components
and common facilities of the Building as may be necessary to keep them in good
and serviceable condition and repair; and

     5.1.4  Quiet Enjoyment - That Landlord has the right to make this Lease and
that Tenant on paying the rent and performing its obligations hereunder shall
peacefully and quietly have, hold and enjoy the Premises throughout the Term
without any manner of hindrance or molestation from Landlord or anyone claiming
under Landlord, subject however to all the terms and provisions hereof;

     5.1.5  Insurance - During the Term, Landlord shall maintain a policy or
policies of insurance covering loss or damage to the Premises, which shall
include such protection (i) as would normally be included for properties like
the Building and (ii) as is required by Landlord's lender.  Such insurance shall
be in an amount at least equal to the full replacement cost of the Premises.
All proceeds under such policies shall be payable exclusively to Landlord or
Landlord's lender.

5.2 INTERRUPTIONS.

     Except with respect to the gross negligence or willful misconduct of
Landlord, Landlord shall not be liable to Tenant for any compensation or
reduction of rent by reason of inconvenience or annoyance or for loss of
business arising from power losses or shortages or from the necessity of
Landlord's entering the Premises for any of the purposes in this Lease
authorized, or for repairing the Premises or any portion

                                      -17-
<PAGE>
 
of the Building or Lot. In case Landlord is prevented or delayed from making any
repairs, alterations or improvements, or furnishing any service or performing
any other covenant or duty to be performed on Landlord's part, by reason of any
cause beyond Landlord's reasonable control, Landlord shall not be liable to
Tenant therefor, nor, except as expressly otherwise provided in Article VII,
shall Tenant be entitled to any abatement or reduction of rent by reason
thereof, nor shall the same give rise to a claim in Tenant's favor that such
failure constitutes actual or constructive total or partial, eviction from the
Premises.

     Landlord reserves the right to stop any service or utility system when
necessary by reason of accident or emergency or until necessary repairs have
been completed.  Except in case of emergency repairs, Landlord will give Tenant
reasonable advance notice of any contemplated stoppage and will use reasonable
efforts to avoid unnecessary inconvenience to Tenant by reason thereof.

     Landlord also reserves the right to institute such reasonable policies,
programs and measures as may be necessary, required or expedient for the
conservation or preservation of energy or energy services or as may be necessary
or required to comply with applicable codes, rules, regulations or standards.


                                  ARTICLE VI

                              TENANT' S COVENANTS

6.1 TENANT' S COVENANTS DURING THE TERM.

     Tenant covenants during the Term and such further time as Tenant occupies
any part of the Premises:

     6.1.1 Tenant's Payments - To pay when due (a) all Annual Rent and
additional rent, (b) all taxes which may be imposed on Tenant's personal
property in the Premises (including, without limitation, Tenant's fixtures and
equipment) regardless to whomever assessed, (c) all charges by public utilities
for telephone and other utility services (including service inspections
therefor) rendered to the Premises not otherwise required hereunder to be
furnished by Landlord without charge and not consumed in connection with any
services required to be furnished by Landlord without charge, and (d) as
additional rent, all charges to Landlord for services rendered pursuant to
Section 5.1.2 hereof.

     6.1.2 Repairs and Yielding Up - Except as otherwise provided in Article VII
and Section 5.1.3, to keep the Premises in good order, repair and condition,
reasonable wear only excepted; and at the expiration or termination of this
Lease peaceably to yield up the Premises and all changes and additions therein
in such

                                      -18-
<PAGE>
 
order, repair and condition, first removing all goods and effects of Tenant and
any items, the removal of which is required by agreement or specified herein to
be removed at Tenant's election and which Tenant elects to remove, and repairing
all damage caused by such removal and restoring the Premises and leaving them
clean and neat.

     6.1.3  Occupancy and Use - Continuously from the Commencement Date, to use
and occupy the Premises only for the Permitted Uses; not to injure or deface the
Premises, Building, or Lot; and not to permit in the Premises any use thereof
which is improper, offensive, contrary to law or ordinances, or liable to create
a nuisance or to invalidate or increase the premiums for any insurance on the
Building or its contents or liable to render necessary any alteration or
addition to the Building; not to dump, flush, or in any way introduce any
hazardous substances or any other toxic substances into the septic, sewage or
other waste disposal system serving the Premises, not to generate, store or
dispose of hazardous substances in or on the Premises or dispose of hazardous
substances from the Premises to any other location without the prior written
consent of Landlord and then only in compliance with the Resource Conservation
and Recovery Act of 1976, as amended, 42 U.S.C. (S)6901 et seq., and all other
applicable laws, ordinances and regulations; to notify Landlord of any incident
which would require the filing of a notice under applicable federal, state, or
local law; not to store or dispose of hazardous substances on the Premises
without first submitting to Landlord a list of all such hazardous substances and
all permits required therefor and thereafter providing to Landlord on an annual
basis Tenant's certification that all such permits have been renewed with copies
of such renewed permits; and to comply with the orders and regulations of all
governmental authorities with respect to zoning, building, fire, health and
other codes, regulations, ordinances or laws applicable to the Premises.
"Hazardous substances" as used in this paragraph shall mean "hazardous
substances" as defined in the Comprehensive Environmental Response Compensation
and Liability Act of 1980, as amended, 42 U.S.C. (S)9601 and regulations adopted
pursuant to said Act.

     6.1.4  Rules and Regulations - To comply with the Rules and Regulations set
forth in Exhibit C and all other reasonable Rules and Regulations hereafter made
by Landlord, of which Tenant has been given notice, for the care and use of the
Building and Lot and their facilities and approaches, it being understood that,
subject to the provisions at Section 5.1.4, Landlord shall not be liable to
Tenant for the failure of other tenants of the Building to conform to such Rules
and Regulations.

     6.1.5  Safety Appliances - To keep the Premises equipped with all safety
appliances required by law or ordinance or any other regulation of any public
authority because of any use made by Tenant and to procure all licenses and
permits so required because of such use and, if requested by Landlord, to do any
work so required because of such use, it being understood that the foregoing
provisions shall not be construed to broaden in any way Tenant's Permitted Uses.

                                      -19-
<PAGE>
 
     6.1.6  Assignment and Subletting - Not without the prior written consent of
Landlord to assign this Lease, which consent shall not be unreasonably withheld
or delayed, to make any sublease, or to permit occupancy of the Premises or any
part thereof by anyone other than Tenant, voluntarily or by operation of law (it
being understood that in no event shall Landlord consent to any such assignment,
sublease or occupancy if the same is on terms more favorable to the successor
occupant than to the then occupant); as additional rent, to reimburse Landlord
promptly for reasonable legal and other expenses incurred by Landlord in
connection with any request by Tenant for consent to assignment or subletting;
no assignment or subletting shall affect the continuing primary liability of
Tenant (which, following assignment, shall be joint and several with the
assignee); no consent to any of the foregoing in a specific instance shall
operate as a waiver in any subsequent instance. Landlord's consent to any
proposed assignment or subletting is required both as to the terms and
conditions thereof, and as to the creditworthiness of the proposed assignee or
subtenant and the consistency of the proposed assignee's or subtenant's business
with other uses and tenants in the Building.  Landlord's consent to assignment
or subletting by Tenant shall not be unreasonably withheld, provided that Tenant
is not then in default under this Lease.  In the event that any assignee or
subtenant pays to Tenant any amounts in excess of the Annual Rent and additional
rent then payable hereunder, or pro rata portion thereof on a square footage
basis for any portion of the Premises, Tenant shall promptly pay said excess
(net of reasonable costs incurred by Tenant in entering into such sublease or
assignment) to Landlord as and when received by Tenant.  If Tenant requests
Landlord's consent to assign this Lease or sublet more than 50% of the Premises,
Landlord shall have the option, exercisable by written notice to Tenant given
within 10 days after receipt of such request, to terminate this Lease with
respect to the entire Premises in the case of a proposed assignment or a
sublease of the entire Premises or with respect to the portion of the Premises
proposed to be sublet in the case of a proposed sublease of less than the entire
Premises, such termination to be effective as of a date specified in such notice
which shall be not less than 30 or more than 60 days after the date of such
notice.

     If, at any time during the Term of this Lease, Tenant is:

          (i)   a corporation or a trust (whether or not having shares of
beneficial interest) and there shall occur any change in the identity of the
majority of the persons then having power to participate in the election or
appointment of the directors, trustees or other persons exercising like
functions and managing the affairs of Tenant; or

          (ii)  a partnership or association or otherwise not a natural person
(and is not a corporation or a trust) and there shall occur any change in the
identity 

                                      -20-
<PAGE>
 
of any of the persons who then are members of such partnership or association or
who comprise Tenant;

Tenant shall so notify Landlord and Landlord may terminate this Lease by notice
to Tenant given within 90 days thereafter if, in Landlord's reasonable judgment,
the financial creditworthiness of Tenant is thereby impaired.  This paragraph
shall not apply if the initial Tenant named herein is a corporation and the
outstanding voting stock thereof is listed on a recognized securities exchange.

     6.1.7 Indemnity - To defend, with counsel approved by Landlord, which
appeal shall not be unreasonably withheld or delayed, all actions against
Landlord, any partner, trustee, stockholder, officer, director, employee or
beneficiary of Landlord, holders of mortgages secured by the Premises or the
Building and Lot and any other party having an interest in the Premises
("Indemnified Parties") with respect to, and to pay, protect, indemnify and save
harmless, to the extent permitted by law, all Indemnified Parties from and
against, any and all liabilities, losses damages, costs, expenses (including
reasonable attorneys' fees and expenses), causes of action, suits, claims,
demands or judgments of any nature (a) to which any Indemnified Party is subject
because of its estate or interest in the Premises, or (b) arising from (i)
injury to or death of any person, or damage to or loss of property, on the
Premises or on adjoining sidewalks, streets or ways, or connected with the use,
condition or occupancy of any thereof unless caused by the negligence of
Landlord or its servants or agents, (ii) violation of this Lease, or (iii) any
act, fault, omission, or other misconduct of Tenant or its agents, contractors,
licensees, sublessees or invitees.

     6.1.8 Tenant's Liability Insurance - To maintain public liability insurance
on the Premises indemnifying Landlord and Tenant against all claims and demands
for (i) injury to or death of any person or damage to or loss of property, on
the Premises or adjoining walks, streets or ways, or connected with the use,
condition or occupancy of any thereof unless caused by the negligence of
Landlord or its servants or agents, (ii) violation of this Lease, or (iii) any
act, fault or omission, or other misconduct of Tenant or its agents,
contractors, licensees, sublessees or invitees, in amounts which shall, at the
beginning of the Term, be at least equal to the limits set forth in Section 1.1,
and from time to time during the Term, shall be for such higher limits, if any,
as are customarily carried in the area in which the Premises are located on
property similar to the Premises and used for similar purposes, and shall be
written on the "Occurrence Basis" and include Host Liquor liability insurance,
as reasonably necessary, and to furnish Landlord with certificates thereof.

     6.1.9  Tenant's Worker's Compensation Insurance - To keep all of Tenant's
employees working in the Premises covered by worker's compensation insurance in
statutory amounts and to furnish Landlord with certificates thereof.

                                      -21-
<PAGE>
 
     6.1.10 Landlord's Right of Entry - To permit Landlord and Landlord's agents
entry: to examine the Premises at reasonable times and, if Landlord shall so
elect, to make repairs or replacements; to remove, at Tenant's expense, any
changes, additions, signs, curtains, blinds, shades, awnings, aerials,
flagpoles, or the like not consented to in writing; and to show the Premises to
prospective tenants during the 12 months preceding expiration of the Term and to
prospective purchasers and mortgagees at all reasonable times.

     6.1.11 Loading - Not to place Tenant's Property, as defined in Section
6.1.13, upon the Premises so as to exceed a rate of 60 pounds of live load per
square foot and not to move any safe, vault or other heavy equipment in, about
or out of the Premises except in such manner and at such times as Landlord shall
in each instance approve; Tenant's business machines and mechanical equipment
which cause vibration or noise that may be transmitted to the Building structure
or to any other leased space in the Building shall be placed and maintained by
Tenant in settings of cork, rubber, spring, or other types of vibration
eliminators sufficient to eliminate such vibration or noise.

     6.1.12 Landlord's Costs - In case Landlord shall be made party to any
litigation commenced by or against Tenant or by or against any parties in
possession of the Premises or any part thereof claiming under Tenant and to the
extent Landlord prevails in such litigation, to pay, as additional rent, all
costs including, without implied limitation, reasonable counsel fees incurred by
or imposed upon Landlord in connection with such litigation and, as additional
rent, also to pay all such costs and fees incurred by Landlord in connection
with the successful enforcement by Landlord of any obligations of Tenant under
this Lease.

     6.1.13 Tenant's Property - All the furnishings, fixtures, equipment,
effects and property of every kind, nature and description of Tenant and of all
persons claiming by, through or under Tenant which, during the continuance of
this Lease or any occupancy of the Premises by Tenant or anyone claiming under
Tenant, may be on the Premises or elsewhere in the Building or on the Lot shall
be at the sole risk and hazard of Tenant, and if the whole or any part thereof
shall be destroyed or damaged by fire, water or otherwise, or by the leakage or
bursting of water pipes, steam pipes, or other pipes, by theft, or from any
other cause, no part of said loss or damage is to be charged to or to be borne
by Landlord unless due to the gross negligence of Landlord.

     6.1.14 Labor or Materialmen's Liens - To pay promptly when due the entire
cost of any work done on the Premises by Tenant, its agents, employees, or
independent contractors; not to cause or permit any liens for labor or materials
performed or furnished in connection therewith to attach to the Premises; and
immediately to discharge any such liens which may so attach.

                                      -22-
<PAGE>
 
     6.1.15 Changes or Additions - Not to make any changes or additions to the
Premises without Landlord's prior written consent, which consent shall not be
unreasonably withheld or delayed, provided that Tenant shall reimburse Landlord
for all out-of-pocket costs incurred by Landlord in reviewing Tenant's proposed
changes or additions, and provided further that, in order to protect the
functional integrity of the Building, all such changes and additions shall be
performed by contractors approved by Landlord, which approval shall not be
unreasonably withheld or delayed.

     6.1.16 Holdover - To pay to Landlord the greater of 150% of (a) the then
fair market rent as conclusively determined by Landlord or (b) the total of the
Annual Rent and additional rent then applicable for each month or portion
thereof Tenant shall retain possession of the Premises or any part thereof after
the termination of this Lease, whether by lapse of time or otherwise, and also
to pay all damages sustained by Landlord on account thereof; the provisions of
this subsection shall not operate as a waiver by Landlord of the right of re-
entry provided in this Lease; at the option of Landlord exercised by a written
notice given to Tenant while such holding over continues, such holding over
shall constitute an extension of this Lease for a period of one year.

                                  ARTICLE VII

                              CASUALTY AND TAKING

7.1 CASUALTY AND TAKING

     In case during the Term all or any substantial part of the Premises,
Building, or Lot or any one or more of them, are damaged materially by fire or
any other cause or by action of public or other authority in consequence thereof
or are taken by eminent domain or Landlord receives compensable damage by reason
of anything lawfully done in pursuance of public or other authority, this Lease
shall terminate at Landlord's election, which may be made, notwithstanding
Landlord's entire interest may have been divested, by notice to Tenant within 30
days after the occurrence of the event giving rise to the election to terminate,
which notice shall specify the effective date of termination which shall be not
less than 30 nor more than 60 days after the date of notice of such termination.
If in any such case the Premises are rendered unfit for use and occupation and
the Lease is not so terminated, Landlord shall use due diligence to put the
Premises, or, in case of a taking, what may remain thereof (excluding any items
installed or paid for by Tenant which Tenant may be required or permitted to
remove) into proper condition for use and occupation to the extent permitted by
the net award of insurance or damages available to Landlord, and a just
proportion of the Annual Rent and additional rent according to the nature and
extent of the injury shall be abated until the Premises or such remainder shall
have been put by Landlord in such condition; and in case of a taking which

                                      -23-
<PAGE>
 
permanently reduces the area of the Premises, a just proportion of the Annual
Rent and additional rent shall be abated for the remainder of the Term and an
appropriate adjustment shall be made to the Annual Estimated Operating Expenses.
In the event the Premises are not restored within 150 days from the date of such
casualty, Tenant shall have the right to terminate this Lease upon notice given
to Landlord within thirty (30) days after the expiration of such 150 day period.

7.2 RESERVATION OF AWARD.

     Landlord reserves to itself any and all rights to receive awards made for
damages to the Premises, Building or Lot and the leasehold hereby created, or
any one or more of them, accruing by reason of exercise of eminent domain or by
reason of anything lawfully done in pursuance of public or other authority.
Tenant hereby releases and assigns to Landlord all Tenant's rights to such
awards, and covenants to deliver such further assignments and assurances thereof
as Landlord may from time to time request, and hereby irrevocably designates and
appoints Landlord its attorney-in-fact to execute and deliver in Tenant's name
and behalf all such further assignments thereof.  It is agreed and understood,
however, that Landlord does not reserve to itself, and Tenant does not assign to
Landlord, any damages payable for (i) movable trade fixtures installed by Tenant
or anybody claiming under Tenant, at its own expense or (ii) relocation expenses
recoverable by Tenant from such authority in a separate action.


                                 ARTICLE VIII

                              RIGHTS OF MORTGAGEE

8.1 PRIORITY OF LEASE.

     This Lease is and shall continue to be subject and subordinate to any
presently existing mortgage or deed of trust of record covering the Lot or
Building or both (the "mortgaged premises").  The holder of any such presently
existing mortgage or deed of trust shall have the election to subordinate the
same to the rights and interests of Tenant under this Lease exercisable by
filing with the appropriate recording office a notice of such election,
whereupon the Tenant's rights and interests hereunder shall have priority over
such mortgage or deed of trust.

     Unless the option provided for in the next following sentence shall be
exercised, this Lease shall be superior to and shall not be subordinate to, any
mortgage, deed of trust or other voluntary lien hereafter placed on the
mortgaged premises.  The holder of any such mortgage, deed of trust or other
voluntary lien shall have the option to subordinate this Lease to the same,
provided that such holder enters into an agreement with Tenant by the terms of
which the holder will 

                                      -24-
<PAGE>
 
agree to recognize the rights of Tenant under this Lease and to accept Tenant as
tenant of the Premises under the terms and conditions of this Lease in the event
of acquisition of title by such holder through foreclosure proceedings or
otherwise and Tenant will agree to recognize the holder of such mortgage as
Landlord in such event, which agreement shall be made to expressly bind and
inure to the benefit of the successors and assigns of Tenant and of the holder
and upon anyone purchasing the mortgaged premises at any foreclosure sale. Any
such mortgage to which this Lease shall be subordinated may contain such terms,
provisions and conditions as the holder deems usual or customary.

8.2 RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S LIABILITY.

     The word "mortgage" as used herein includes mortgages, deeds of trust or
other similar instruments evidencing other voluntary liens or encumbrances, and
modifications, consolidations, extensions, renewals, replacements and
substitutes thereof.  The word "holder" shall mean a mortgagee, and any
subsequent holder or holders of a mortgage.  Until the holder of a mortgage
shall enter and take possession of the Premises for the purpose of foreclosure,
such holder shall have only such rights of Landlord as are necessary to preserve
the integrity of this Lease as security.  Upon entry and taking possession of
the Premises for the purpose of foreclosure, such holder shall have all the
rights of Landlord.  Notwithstanding any other provision of this Lease to the
contrary, including without limitation Section 10.4, no such holder of a
mortgage shall be liable, either as mortgagee or as assignee, to perform, or be
liable in damages for failure to perform any of the obligations of Landlord
unless and until such holder shall enter and take possession of the Premises for
the purpose of foreclosure, and such holder shall not in any event be liable to
perform or for failure to perform the obligations of Landlord under Section 3.1.
Upon entry for the purpose of foreclosure, such holder shall be liable to
perform all of the obligations of Landlord (except for the obligations under
Section 3.1), subject to and with the benefit of the provisions of Section 10.4,
provided that a discontinuance of any foreclosure proceeding shall be deemed a
conveyance under said provisions to the owner of the equity of the Premises.

8.3 MORTGAGEE'S ELECTION.

     Notwithstanding any other provision to the contrary contained in this
Lease, if prior to substantial completion of Landlord's obligations under
Article III, any holder of a first mortgage on the mortgaged premises enters and
takes possession thereof for the purpose of foreclosing the mortgage, such
holder may elect, by written notice given to Tenant and Landlord at any time
within 90 days after such entry and taking of possession, not to perform
Landlord's obligations under Article III, and in such event such holder and all
persons claiming under it shall be relieved of all obligations to perform, and
all liability for failure to perform, said Landlord's obligations under 

                                      -25-
<PAGE>
 
Article III, and Tenant may terminate this Lease and all its obligations
hereunder by written notice to Landlord and such holder given within 30 days
after the day on which such holder shall have given its notice as aforesaid.

8.4 NO PREPAYMENT OR MODIFICATION, ETC.

     Tenant shall not pay Annual Rent, additional rent, or any other charge more
than 10 days prior to the due date thereof, provided, however, that not more
than once during each calendar year included in the Term, Tenant may prepay any
portion of the Annual Rent, additional rent or other charges due and payable
under this Lease, provided such prepayment is made with respect to Annual Rent,
additional rent and other charges due and payable in the calendar year in which
the prepayment is to be received by Landlord.  Except for the foregoing, no
prepayment of Annual Rent, additional rent or other charge, no assignment of
this Lease and no agreement to modify so as to reduce the rent, change the Term,
or otherwise materially change the rights of Landlord under this Lease, or to
relieve Tenant of any obligations or liability under this Lease, shall be valid
unless consented to in writing by Landlord's mortgagees of record, if any.

8.5 NO RELEASE OR TERMINATION.

     No act or failure to act on the part of Landlord which would entitle Tenant
under the terms of this Lease, or by law, to be relieved of Tenant's obligations
hereunder or to terminate this Lease, shall result in a release or termination
of such obligations or a termination of this Lease unless (i) Tenant shall have
first given written notice of Landlord's act or failure to act to Landlord's
mortgagees of record, if any, specifying the act or failure to act on the part
of Landlord which could or would give basis to Tenant's rights and (ii) such
mortgagees, after receipt of such notice, have failed or refused to correct or
cure the condition complained of within a reasonable time thereafter, but
nothing contained in this Section 8.5 shall be deemed to impose any obligation
on any such mortgagee to correct or cure any such condition.  "Reasonable time"
as used above means and includes a reasonable time to obtain possession of the
mortgaged premises, if the mortgagee elects to do so, and a reasonable time to
correct or cure the condition if such condition is determined to exist.

8.6 CONTINUING OFFER.

     The covenants and agreements contained in this Lease with respect to the
rights, powers and benefits of a mortgagee (particularly, without limitation
thereby, the covenants and agreements contained in this Article VIII) constitute
a continuing offer to any person, corporation or other entity, which by
accepting or requiring an assignment of this Lease or by entry or foreclosure
assumes the obligations herein set forth with respect to such mortgagee; such
mortgagee is hereby constituted a party to 

                                      -26-
<PAGE>
 
this Lease as an obligee hereunder to the same extent as though its name were
written hereon as such; and such mortgagee shall be entitled to enforce such
provisions in its own name. Tenant agrees on request of Landlord to execute and
deliver from time to time any agreement which may reasonably be deemed necessary
to implement the provisions of this Article VIII.

8.7 MORTGAGEE'S APPROVAL.

     Landlord's obligation to perform its covenants and agreements hereunder is
subject to the condition precedent that this Lease be approved by the holder of
any mortgage of which the Premises are a part and by the issuer of any
commitment to make a mortgage loan which is in effect on the date hereof.
Unless Landlord gives Tenant written notice within 30 business days after the
date hereof that such holder or issuer, or both, disapprove this Lease, then
this condition shall be deemed to have been satisfied or waived and the
provisions of this Section 5.7 shall be of no further force or effect.


                                  ARTICLE IX

                                    DEFAULT

9.1 EVENTS OF DEFAULT.

     If any default by Tenant continues after notice, in case of Annual Rent,
additional rent, Tenant Improvement Reimbursement or any other monetary
obligation to Landlord for more than 10 days, or in any other case for more than
30 days and such additional time, if any, as is reasonably necessary to cure the
default if the default is of such a nature that it cannot reasonably be cured in
30 days and Tenant diligently endeavors to cure such default; or if Tenant
becomes insolvent, fails to pay its debts as they fall due, files a petition
under any chapter of the U.S. Bankruptcy Code, 11 U.S.C. 101 et seq., as it may
be amended (or any similar petition under any insolvency law of any
jurisdiction), or if such petition is filed against Tenant; or if Tenant
proposes any dissolution, liquidation, composition, financial reorganization or
recapitalization with creditors, makes an assignment or trust mortgage for
benefit of creditors, or if a receiver, trustee, custodian or similar agent is
appointed or takes possession with respect to any property of Tenant; or if the
leasehold hereby created is taken on execution or other process of law in any
action against Tenant; then, and in any such case, Landlord and the agents and
servants of Landlord may, in addition to and not in derogation of any remedies
for any preceding breach of covenant, immediately or at any time thereafter
while such default continues and without further notice, at Landlord's election,
do any one or more of the following: (1) give Tenant written notice stating that
the Lease is terminated, effective upon the giving of such notice or upon a date
stated in such 

                                      -27-
<PAGE>
 
notice, as Landlord may elect, in which event the Lease shall be irrevocably
extinguished and terminated as stated in such notice without any further action,
or (2) with or without process of law, in a lawful manner enter and repossess
the Premises as of Landlord's former estate, and expel Tenant and those claiming
through or under Tenant, and remove its and their effects, without being guilty
of trespass, in which event the Lease shall be irrevocably extinguished and
terminated at the time of such entry, or (3) pursue any other rights or remedies
permitted by law. Any such termination of the Lease shall be without prejudice
to any remedies which might otherwise be used for arrears of rent or prior
breach of covenant, and in the event of such termination Tenant shall remain
liable under this Lease as hereinafter provided. Tenant hereby waives all
statutory rights (including, without limitation, rights of redemption, if any)
to the extent such rights may be lawfully waived, and Landlord, without notice
to Tenant, may store Tenant's effects and those of any person claiming through
or under Tenant at the expense and risk of Tenant and, if Landlord so elects,
may sell such effects at public auction or private sale and apply the net
proceeds to the payment of all sums due to Landlord from Tenant, if any, and pay
over the balance, if any, to Tenant.

9.2 TENANT'S OBLIGATIONS AFTER TERMINATION.

     In the event that this Lease is terminated under any of the provisions
contained in Section 9.1 or shall be otherwise terminated for breach of any
obligation of Tenant, Tenant covenants to pay forthwith to Landlord, as
compensation, the excess of the total rent reserved for the residue of the Term
over the rental value of the Premises for said residue of the Term.  In
calculating the rent reserved, there shall be included, in addition to the
Annual Rent and all additional rent, the value of all other consideration agreed
to be paid or performed by Tenant for said residue. Tenant further covenants as
an additional and cumulative obligation after any such ending to pay punctually
to Landlord all the sums and perform all the obligations which Tenant covenants
in this Lease to pay and to perform in the same manner and to the same extent
and at the same time as if this Lease had not been terminated.  In calculating
the amounts to be paid by Tenant under the next foregoing covenant, Tenant shall
be credited with any amount paid to Landlord as compensation as provided in the
first sentence of this Section 9.2 and also with the net proceeds of any rents
obtained by Landlord by reletting the Premises, after deducting all Landlord's
expenses in connection with such reletting, including, without implied
limitation, all repossession costs, brokerage commissions, fees for legal
services and expenses of preparing the Premises for such reletting, it being
agreed by Tenant that Landlord may (i) relet the Premises or any part or parts
thereof for a term or terms which may at Landlord's option be equal to or less
than or exceed the period which would otherwise have constituted the balance of
the Term and may grant such concessions and free rent as Landlord in its sole
judgment considers advisable or necessary to relet the same and (ii) make such
alterations, repairs and decorations in the Premises as Landlord in its sole
judgment considers advisable or necessary to relet the same, 

                                      -28-
<PAGE>
 
and no action of Landlord in accordance with the foregoing or failure to relet
or to collect rent under reletting shall operate or be construed to release or
reduce Tenant's liability as aforesaid.

     So long as at least 12 months of the Term remain unexpired at the time of
such termination, in lieu of any other damages or indemnity and in lieu of full
recovery by Landlord of all sums payable under all the foregoing provisions of
this Section 9.2, Landlord may by written notice to Tenant, at any time after
this Lease is terminated under any of the provisions contained in Section 9.1,
or is otherwise terminated for breach of any obligation of Tenant and before
such full recovery, elect to recover and Tenant shall thereupon pay, as
liquidated damages, an amount equal to the aggregate of the Annual Rent and
additional rent accrued under Article IV in the 12 months ended next prior to
such termination plus the amount of Annual Rent and additional rent of any kind
accrued and unpaid at the time of termination and less the amount of any
recovery by Landlord under the foregoing provisions of this Section 9.2 up to
the time of payment of such liquidated damages.

     Nothing contained in this Lease shall, however, limit or prejudice the
right of Landlord to prove and obtain in proceedings for bankruptcy or
insolvency by reason of the termination of this Lease, an amount equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in which, the damages are to be proved, whether or not
the amount be greater, equal to, or less than the amount of the loss or damages
referred to above.


                                   ARTICLE X

                                 MISCELLANEOUS

10.1 NOTICE OF LEASE.

     Upon request of either party, both parties shall execute and deliver, after
the Term begins, a short form of this Lease in form appropriate for recording or
registration, and if this Lease is terminated before the Term expires, an
instrument in such form acknowledging the date of termination.

10.2 Intentionally Deleted

10.3 NOTICES FROM ONE PARTY TO THE OTHER.

     All notices required or permitted hereunder shall be in writing and
addressed, if to the Tenant, at Tenant's Address or such other address as Tenant
shall have last designated by notice in writing to Landlord and, if to Landlord,
at Landlord's Address or such other address as Landlord shall have last
designated by notice in 

                                      -29-
<PAGE>
 
writing to Tenant. Any notice shall have been deemed duly given if mailed to
such address postage prepaid, registered or certified mail, return receipt
requested, when deposited with the U.S. Postal Service, or if delivered to such
address by hand, when so delivered.

10.4 BIND AND INURE.

     The obligations of this Lease shall run with the land, and this Lease shall
be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns, except that the Landlord named herein and
each successive owner of the Premises shall be liable only for the obligations
accruing during the period of its ownership.  The obligations of Landlord shall
be binding upon the assets of Landlord which comprise the Premises but not upon
other assets of Landlord.  No individual partner, trustee, stockholder, officer,
director, employee or beneficiary of Landlord shall be personally liable under
this Lease and Tenant shall look solely to Landlord's interest in the Premises
in pursuit of its remedies upon an event of default hereunder, and the general
assets of the individual partners, trustees, stockholders, officers, employees
or beneficiaries of Landlord shall not be subject to levy, execution or other
enforcement procedure for the satisfaction of the remedies of Tenant.

10.5 NO SURRENDER.

     The delivery of keys to any employee of Landlord or to Landlord's agent or
any employee thereof shall not operate as a termination of this Lease or a
surrender of the Premises.

10.6 NO WAIVER, ETC.

     The failure of Landlord or of Tenant to seek redress for violation of, or
to insist upon the strict performance of any covenant or condition of this Lease
or, with respect to such failure of Landlord, any of the Rules and Regulations
referred to in Section 6.1.4, whether heretofore or hereafter adopted by
Landlord, shall not be deemed a waiver of such violation nor prevent a
subsequent act, which would have originally constituted a violation, from having
all the force and effect of an original violation, nor shall the failure of
Landlord to enforce any of said Rules and Regulations against any other tenant
in the Building be deemed a waiver of any such Rules or Regulations.  The
receipt by Landlord of Annual Rent or additional rent with knowledge of the
breach of any covenant of this Lease shall not be deemed a waiver of such breach
by Landlord, unless such waiver be in writing and signed by Landlord.  No
consent or waiver, express or implied, by Landlord or Tenant to or of any breach
of any agreement or duty shall be construed as a waiver or consent to or of any
other breach of the same or any other agreement or duty.

                                      -30-
<PAGE>
 
10.7 NO ACCORD AND SATISFACTION.

     No acceptance by Landlord of a lesser sum than the Annual Rent and
additional rent then due shall be deemed to be other than on account of the
earliest installment of such rent due, nor shall any endorsement or statement on
any check or any letter accompanying any check or payment as rent be deemed as
accord and satisfaction, and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such installment or
pursue any other remedy in this Lease provided.

10.8 CUMULATIVE REMEDIES.

     The specific remedies to which Landlord may resort under the terms of this
Lease are cumulative and are not intended to be exclusive of any other remedies
or means of redress to which it may be lawfully entitled in case of any breach
or threatened breach by Tenant of any provisions of this Lease.  In addition to
the other remedies provided in this Lease, Landlord shall be entitled to the
restraint by injunction of the violation or attempted or threatened violation of
any of the covenants, conditions or provisions of this Lease or to a decree
compelling specific performance of any such covenants, conditions or provisions.

10.9 LANDLORD'S RIGHT TO CURE.

     If Tenant shall at any time default in the performance of any obligation
under this Lease, Landlord shall have the right, but shall not be obligated, to
enter upon the Premises and to perform such obligation, notwithstanding the fact
that no specific provision for such substituted performance by Landlord is made
in this Lease with respect to such default.  In performing such obligation,
Landlord may make any payment of money or perform any other act.  All sums so
paid by Landlord (together with interest at the rate of 4% per annum in excess
of the then average prime commercial rate of interest being charged by the three
largest national banks in Boston, Massachusetts) and all necessary incidental
costs and expenses in connection with the performance of any such act by
Landlord, shall be deemed to be additional rent under this Lease and shall be
payable to Landlord immediately on demand. Landlord may exercise the foregoing
rights without waiving any other of its rights or releasing Tenant from any of
its obligations under this Lease.

10.10 ESTOPPEL CERTIFICATE.

     Tenant agrees, from time to time, upon not less than 15 days' prior written
request by Landlord, to execute, acknowledge and deliver to Landlord a statement
in writing certifying that this Lease is unmodified and in full force and
effect; that Tenant has no defenses, offsets or counterclaims against its
obligations to pay the Annual Rent and additional rent and to perform its other
covenants under this Lease; 

                                      -31-
<PAGE>
 
that there are no uncured defaults of Landlord or Tenant under this Lease (or,
if there have been modifications, that this Lease is in full force and effect as
modified and stating the modifications, and, if there are any defenses, offsets,
counterclaims, or defaults, setting them forth in reasonable detail); and the
dates to which the Annual Rent, additional rent and other charges have been
paid. Any such statement delivered pursuant to this Section 10.10 shall be in a
form reasonably acceptable to and may be relied upon by any prospective
purchaser or mortgagee of premises which include the Premises or any prospective
assignee of any such mortgagee.

10.11 WAIVER OF SUBROGATION.

     Any insurance carried by either party with respect to the Premises and
property therein or occurrences thereon shall include a clause or endorsement
denying to the insurer rights of subrogation against the other party to the
extent rights have been waived by the insured prior to occurrences of injury or
loss. Each party, notwithstanding any provisions of this Lease to the contrary,
hereby waives any rights of recovery against the other for injury or loss due to
hazards covered by insurance containing such clause or endorsement to the extent
of the indemnification received thereunder.

10.12 ACTS OF GOD.

     In any case where either party hereto is required to do any act, delays
caused by or resulting from Acts of God, war, civil commotion, fire, flood or
other casualty, labor difficulties, shortages of labor, materials or equipment,
government regulations, unusually severe weather, or other causes beyond such
party's reasonable control shall not be counted in determining the time during
which work shall be completed, whether such time be designated by a fixed date,
a fixed time or a "reasonable time", and such time shall be deemed to be
extended by the period of such delay.

10.13 BROKERAGE.

     Tenant represents and warrants that it has dealt with no broker in
connection with this transaction other than Spaulding and Slye Colliers Limited
Partnership and agrees to defend, with counsel approved by Landlord, indemnify
and save Landlord harmless from and against any and all cost, expense or
liability for any compensation, commissions or charges claimed by a broker or
agent, other than Spaulding and Slye Colliers Limited Partnership, with respect
to Tenant's dealings in connection with this Lease.

10.14 SUBMISSION NOT AN OFFER.

     The submission of a draft of this Lease or a summary of some or all of its
provisions does not constitute an offer to lease or demise the Premises, it
being 

                                      -32-
<PAGE>
 
understood and agreed that neither Landlord nor Tenant shall be legally bound
with respect to the leasing of the Premises unless and until this Lease has been
executed by both Landlord and Tenant and a fully executed copy has been
delivered to each of them.

10.15 APPLICABLE LAW AND CONSTRUCTION.

     This Lease shall be governed by and construed in accordance with the laws
of the state in which the Premises are located.  If any term, covenant,
condition or provision of this Lease or the application thereof to any person or
circumstances shall be declared invalid or unenforceable by the final ruling of
a court of competent jurisdiction having final review, the remaining terms,
covenants, conditions and provisions of this Lease and their application to
persons or circumstances shall not be affected thereby and shall continue to be
enforced and recognized as valid agreements of the parties, and in the place of
such invalid or unenforceable provision, there shall be substituted a like, but
valid and enforceable provision which comports to the findings of the aforesaid
court and most nearly accomplishes the original intention of the parties.

     There are no oral or written agreements between Landlord and Tenant
affecting this Lease.  This Lease may be amended, and the provisions hereof may
be waived or modified, only by instruments in writing executed by Landlord and
Tenant.

     The titles of the several Articles and Sections contained herein are for
convenience only and shall not be considered in construing this Lease.

     Unless repugnant to the context, the words "Landlord" and "Tenant"
appearing in this Lease shall be construed to mean those named above and their
respective heirs, executors, administrators, successors and assigns, and those
claiming through or under them respectively.  If there be more than one tenant,
the obligations imposed by this Lease upon Tenant shall be joint and several.


                                  ARTICLE XI

                               SECURITY DEPOSIT

     Upon execution of the Lease, Tenant shall provide to Landlord either a cash
deposit in the amount of the Security Deposit or an irrevocable and
unconditional letter of credit in the amount of the Security Deposit (in either
case, the "Security Deposit") issued by a bank or other institution satisfactory
to Landlord in its sole discretion and in a form satisfactory to Landlord in its
sole discretion, naming Landlord, its successors and assigns as the beneficiary
and expiring no sooner than 

                                      -33-
<PAGE>
 
thirty (30) days after the Term Expiration Date (the "Letter of Credit").
Landlord shall be permitted to draw upon the Letter of Credit in the event of
(i) default by Tenant in any of its obligations hereunder, in which event
Landlord may draw upon all or~a portion of the Letter of Credit and apply the
proceeds to cure such default, or (ii) in the event the Tenant exercises its
Option to Extend hereunder, failure by Tenant to provide to Landlord, no less
than 30 days prior to the expiration date of the Letter of Credit then held by
Landlord, a replacement or substitute Letter of Credit in the same amount as the
original Letter of Credit, as it may be reduced hereunder, and otherwise subject
to the conditions set forth above, which expires no sooner than thirty (30) days
after the Term Expiration Date as extended in accordance with Tenant's exercise
of its Option to Extend, in which event Landlord may draw upon all of the Letter
of Credit and hold the cash proceeds thereof as the Security Deposit hereunder.
In either case, the Security Deposit shall be held by Landlord as security,
without interest, for and during the Term and provided no default has occurred
hereunder, the Security Deposit shall be returned to Tenant at the termination
of the Lease. Notwithstanding the foregoing, the Security Deposit shall be
reduced [by $15,000] on January 1, 2000, or as soon as reasonably practicable
thereafter, so long as no default has occurred hereunder and that a substitute
letter of credit is provided to Landlord, if necessary, in the amount of the
Letter of Credit as reduced and otherwise satisfying the conditions set forth
above. If all or any part of the Security Deposit is applied to an obligation of
Tenant hereunder, Tenant shall immediately upon request by Landlord restore the
Security Deposit to its original amount. Tenant shall not have the right to call
upon Landlord to apply all or any part of the Security Deposit to cure any
default or fulfill any obligation of Tenant, but such use shall be solely in the
discretion of Landlord. Upon any conveyance by Landlord of its interest under
this Lease, the Security Deposit may be delivered by Landlord to Landlord's
grantee or transferee. Upon any such delivery, Tenant hereby releases Landlord
herein named of any and all liability with respect to the Security Deposit, its
application and return, and Tenant agrees to look solely to such grantee or
transferee. It is further understood that this provision shall also apply to
subsequent grantees and transferees.

     EXECUTED as a sealed instrument in two or more counterparts on the day and
year first above written.

                                      -34-
<PAGE>
 
                                     LANDLORD

                                     TRUSTEES OF LEXINGTON  
                                     DEVELOPMENT COMPANY TRUST
 
                                     By:  Spaulding and Slye Services Limited 
                                          Partnership, authorized agent

                                          By:  Spaulding and Slye Real
                                               Estate Services Company, Inc.
 
 
                                               By:__________________________
                                                    Name:
                                                    Title:
 
 
                                     TENANT:
 
                                     LINKAGE, INC.
 
                                     By:____________________________________
 
                                          Name:_____________________________
                                               (please print or type)
 
                                          Title:____________________________
                                                (please print or type)
 
                                     A copy of Tenant's corporate authorization
                                     for such execution is attached hereto.

                                      -35-
<PAGE>
 
                                  EXHIBIT A-l

            Plan Showing Tenant's Space as of the Commencement Date
            -------------------------------------------------------


[Section intentionally omitted; available upon request to Linkage Solutions,
Inc.]


                                  EXHIBIT A-2

                     Plan Showing Tenant's Space as of the
                     -------------------------------------
                       First Expansion Commencement Date
                       ---------------------------------


[Section intentionally omitted; available upon request to Linkage Solutions,
Inc.]



                                  EXHIBIT A-3

                     Plan Showing Tenant's Space as of the
                     -------------------------------------
                      Second Expansion Commencement Date
                      ----------------------------------

[Section intentionally omitted; available upon request to Linkage Solutions,
Inc.]

<PAGE>
 
                                   EXHIBIT B
                                 25 MALL ROAD

                          BUILDING STANDARD MATERIALS

[Section intentionally omitted; available upon request to Linkage Solutions,
Inc.]



                                   EXHIBIT C
                              LANDLORD'S SERVICES

[Section intentionally omitted; available upon request to Linkage Solutions,
Inc.]