Document:

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                                                                   EXHIBIT 10.19

                                 TIME GUARANTY

                          Dated as of April 25, 2000

                             From c-quential, Inc.

                                 as Guarantor
                                 -- ---------

                                  in favor of

                        THE LENDERS REFERRED TO IN THE
                     AMENDED AND RESTATED CREDIT AGREEMENT
                              REFERRED TO HEREIN
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                              TABLE OF CONTENTS
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                                                                            Page
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<S>            <C>                                                          <C>
Section 1.     Guaranty; Limitation of Liability..........................   1

Section 2.     Automatic Release..........................................   2

Section 3.     Guaranty Absolute..........................................   2

Section 4.     Waivers and Acknowledgements...............................   3

Section 5.     Subrogation................................................   4

Section 6.     Payments Free and Clear of Taxes, Etc......................   5

Section 7.     Representations and Warranties.............................   7

Section 8.     Covenants..................................................   7

Section 9.     Amendments, Etc............................................   8

Section 10.    Notices, Etc...............................................   8

Section 11.    No Waiver, Remedies........................................   8

Section 12.    Right of Set-off...........................................   8

Section 13.    Indemnification............................................   9

Section 14.    Subordination..............................................   9

Section 15.    Continuing Guaranty; Assignments under the Credit
               Agreement..................................................  10

Section 16.    Execution in Counterparts..................................  10

Section 17.    Governing Law; Jurisdiction; Waiver of Jury Trial, Etc.....  11

</TABLE>
<PAGE>

                                 TIME GUARANTY

     TIME GUARANTY dated as of April 25, 2000, made by c-quential, Inc., a
Delaware corporation (the " Guarantor" or "TIME") in favor of the Lenders (as
defined in the Credit Agreement referred to below).

     PRELIMINARY STATEMENTS.  (1) Arthur D. Little, Inc., a Massachusetts
corporation ("ADL" or a "Borrower") and Arthur D. Little International, Inc., a
Massachusetts corporation (a "Borrower" and, together with ADL, the
"Borrowers"), are parties to the Amended and Restated Credit Agreement dated as
of April 25, 2000 (as amended, amended and restated, supplemented or otherwise
modified from time to time, the "Credit Agreement"; the capitalized terms
defined therein and not otherwise defined herein being used herein as therein
defined) with certain Lenders party thereto and Citibank, N.A., as Agent.

     (2) The Borrowers entered into a Credit Agreement dated as of June 22, 1998
(the "Existing Credit Agreement"), with the Initial Lenders (as defined therein)
and the Agent.  Pursuant to the Existing Credit Agreement, the Initial Lenders
made Advances to the Borrowers and, as at the date of this Agreement, Advances
in the aggregate amount of $29,000,000 are outstanding.  The Initial Lenders and
the Borrowers have agreed to amend and restate the Existing Credit Agreement in
order to waive certain defaults under the Existing Credit Agreement and provide
for the repayment of all Advances as provided in the Amended and Restated Credit
Agreement.  It is a condition precedent to the effectiveness of the Amended and
Restated Credit Agreement that the Guarantor shall have executed and delivered
this Guaranty.

     NOW, THEREFORE, in consideration of the premises and in order to induce the
Lenders to enter into the Credit Agreement the Guarantor hereby agrees as
follows:

     Section 1.  Guaranty; Limitation of Liability.
                 ---------------------------------

          (a) Subject to Section 2, the Guarantor hereby absolutely,
unconditionally and irrevocably guarantees the punctual payment when due,
whether at scheduled maturity or on any date of a required prepayment or by
acceleration, demand or otherwise, of all Obligations of each other Loan Party
now or hereafter existing under or in respect of the Loan Documents (including,
without limitation, any extensions, modifications, substitutions, amendments or
renewals of any or all of the foregoing Obligations), whether direct or
indirect, absolute or contingent, and whether for principal, interest, premiums,
fees, indemnities, contract causes of action, costs, expenses or otherwise (such
Obligations being the "Guaranteed Obligations"), and agrees to pay any and all
expenses (including, without limitation, fees and expenses of counsel) incurred
by the Agent or any other Lender in enforcing any rights under this Guaranty, or
any other Loan Document.  Without limiting the generality of the foregoing, the
Guarantor's liability shall extend to all amounts that constitute part of the
Guaranteed Obligations and would be owed by any other Loan Party to any Lender
under or in respect of the Loan Documents but for the fact that they are
unenforceable or not allowable due to the existence of a bankruptcy,
reorganization or similar proceeding involving such other Loan Party.

          (b) The Guarantor, and by its acceptance of this Guaranty, the Agent
and each other Lender, hereby confirms that it is the intention of all such
Persons that this Guaranty and
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the Obligations of the Guarantor hereunder not constitute a fraudulent transfer
or conveyance for purposes of Bankruptcy Law (as hereinafter defined), the
Uniform Fraudulent Conveyance Act, the Uniform Fraudulent Transfer Act or any
similar foreign, federal or state law to the extent applicable to this Guaranty
and the Obligations of the Guarantor hereunder. To effectuate the foregoing
intention, the Agent, the other Lenders and the Guarantor hereby irrevocably
agree that the Obligations of the Guarantor under this Guaranty at any time
shall be limited to the maximum amount as will result in the Obligations of the
Guarantor under this Guaranty not constituting a fraudulent transfer or
conveyance. For purposes hereof, "Bankruptcy Law" means any proceeding of the
type referred to in Section 7.01(e) of the Credit Agreement or Title 11, U.S.
Code, or any similar foreign, federal or state law for the relief of debtors.

          (c) The Guarantor hereby unconditionally and irrevocably agrees that
in the event any payment shall be required to be made to any Lender under this
Guaranty or the ADL Guaranty or any other guaranty, the Guarantor will
contribute, to the maximum extent permitted by law, such amounts so as to
maximize the aggregate amount paid to the Lenders under or in respect of the
Loan Documents.

     Section 2.  Automatic Release.  Notwithstanding any other provision of
                 -----------------
this Guaranty or any other Loan Document to the contrary, the obligations of the
Guarantor hereunder shall be, without notice of any kind, automatically and
forever released and discharged upon a Successful TIME IPO.  For the purpose of
this Section 2, "Successful TIME IPO" means that the Borrowers shall have caused
TIME to file with the Securities and Exchange Commission a registration
statement for the public offering of shares representing not less than 8% of the
common stock of TIME; and shall have caused such registration statement to
become effective and all such shares shall have been sold pursuant to an initial
public offering.

     Section 3.  Guaranty Absolute.  The Guarantor guarantees that the
                 -----------------
Guaranteed Obligations will be paid strictly in accordance with the terms of the
Loan Documents, regardless of any law, regulation or order now or hereafter in
effect in any jurisdiction affecting any of such terms or the rights of any
Lender with respect thereto. The Obligations of the Guarantor under or in
respect of this Guaranty are independent of the Guaranteed Obligations or any
other Obligations of any other Loan Party under or in respect of the Loan
Documents, and a separate action or actions may be brought and prosecuted
against the Guarantor to enforce this Guaranty, irrespective of whether any
action is brought against the Borrowers or any other Loan Party or whether any
Borrower or any other Loan Party is joined in any such action or actions. The
liability of the Guarantor under this Guaranty shall be irrevocable, absolute
and unconditional irrespective of, and the Guarantor hereby irrevocably waives
any defenses it may now have or hereafter acquire in any way relating to, any or
all of the following:

          (a) any lack of validity or enforceability of any Loan Document, or
     any agreement or instrument relating thereto;

          (b) any change in the time, manner or place of payment of, or in any
     other term of, all or any of the Guaranteed Obligations or any other
     Obligations of any other Loan Party under or in respect of the Loan
     Documents, or any other amendment or waiver of or any consent to departure
     from any Loan Document, including, without

                                       2
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     limitation, any increase in the Guaranteed Obligations resulting from the
     extension of additional credit to any Loan Party or any of its Subsidiaries
     or otherwise;

          (c) any taking, exchange, release or non-perfection of any Collateral
     or any other collateral, or any taking, release or amendment or waiver of,
     or consent to departure from, any other guaranty, for all or any of the
     Guaranteed Obligations;

          (d) any manner of application of Collateral or any other collateral,
     or proceeds thereof, to all or any of the Guaranteed Obligations, or any
     manner of sale or other disposition of any Collateral or any other
     collateral for all or any of the Guaranteed Obligations or any other
     Obligations of any Loan Party under the Loan Documents, or any other assets
     of any Loan Party or any of its Subsidiaries;

          (e) any change, restructuring or termination of the corporate
     structure or existence of any Loan Party or any of its Subsidiaries;

          (f) any failure of any Lender to disclose to any Loan Party any
     information relating to the business, condition (financial or otherwise),
     operations, performance, properties or prospects of any other Loan Party
     now or hereafter known to such Lender (the Guarantor waives any duty on the
     part of the Lenders to disclose such information);

          (g) the failure of any other Person to execute or deliver this
     Guaranty, any Guaranty Supplement (as hereinafter defined) or any other
     guaranty or agreement or the release or reduction of liability of any
     Guarantor or other guarantor or surety with respect to the Guaranteed
     Obligations; or

          (h) any other circumstance (including, without limitation, any statute
     of limitations) or any existence of or reliance on any representation by
     any Lender that might otherwise constitute a defense available to, or a
     discharge of, any Loan Party or any other guarantor or surety.

This Guaranty shall continue to be effective or be reinstated, as the case may
be, if at any time any payment of any of the Guaranteed Obligations is rescinded
or must otherwise be returned by any Lender or any other Person upon the
insolvency, bankruptcy or reorganization of any Borrower or any other Loan Party
or otherwise, all as though such payment had not been made.

     Section 4.  Waivers and Acknowledgements.
                 ----------------------------

          (a) The Guarantor hereby unconditionally and irrevocably waives
promptness, diligence, notice of acceptance, presentment, demand for
performance, notice of nonperformance, default, acceleration, protest or
dishonor and any other notice with respect to any of the Guaranteed Obligations
and this Guaranty and any requirement that any Lender protect, secure, perfect
or insure any Lien or any property subject thereto or exhaust any right or take
any action against any Loan Party or any other Person or any Collateral.

          (b) The Guarantor hereby unconditionally and irrevocably waives any
right to revoke this Guaranty and acknowledges that this Guaranty is continuing
in nature and applies to all Guaranteed Obligations, whether existing now or in
the future.

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          (c) The Guarantor hereby unconditionally and irrevocably waives
(i) any defense arising by reason of any claim or defense based upon an election
of remedies by any Lender that in any manner impairs, reduces, releases or
otherwise adversely affects the subrogation, reimbursement, exoneration,
contribution or indemnification rights of the Guarantor or other rights of the
Guarantor to proceed against any of the other Loan Parties, any other guarantor
or any other Person or any Collateral and (ii) any defense based on any right of
set-off or counterclaim against or in respect of the Obligations of the
Guarantor hereunder.

          (d) The Guarantor acknowledges that the Collateral Agent may, without
notice to or demand upon the Guarantor and without affecting the liability of
the Guarantor under this Guaranty, foreclose under any mortgage by nonjudicial
sale, and the Guarantor hereby waives any defense to the recovery by the
Collateral Agent and the other Lenders against the Guarantor of any deficiency
after such nonjudicial sale and any defense or benefits that may be afforded by
applicable law.

          (e) The Guarantor hereby unconditionally and irrevocably waives any
duty on the part of any Lender to disclose to the Guarantor any matter, fact or
thing relating to the business, condition (financial or otherwise), operations,
performance, properties or prospects of any other Loan Party or any of its
Subsidiaries now or hereafter known by such Lender.

          (f) The Guarantor acknowledges that it will receive substantial direct
and indirect benefits from the financing arrangements contemplated by the Loan
Documents, and that the waivers set forth in Section 3 and this Section 4 are
knowingly made in contemplation of such benefits.

     Section 5.  Subrogation.  The Guarantor hereby unconditionally and
                 -----------
irrevocably agrees not to exercise any rights that it may now have or hereafter
acquire against the Borrowers, any other Loan Party or any other insider
guarantor that arise from the existence, payment, performance or enforcement of
the Guarantor's Obligations under or in respect of this Guaranty, or any other
Loan Document, including, without limitation, any right of subrogation,
reimbursement, exoneration, contribution or indemnification and any right to
participate in any claim or remedy of any Lender against the Borrowers, any
other Loan Party or any other insider guarantor or any Collateral, whether or
not such claim, remedy or right arises in equity or under contract, statute or
common law, including, without limitation, the right to take or receive from any
Borrower, any other Loan Party or any other insider guarantor, directly or
indirectly, in cash or other property or by set-off or in any other manner,
payment or security on account of such claim, remedy or right, unless and until
all of the Guaranteed Obligations and all other amounts payable under this
Guaranty shall have been paid in full in cash, and all Letters of Credit shall
have expired or been terminated and the Commitments shall have expired or been
terminated.  If any amount shall be paid to the Guarantor in violation of the
immediately preceding sentence at any time prior to the latest of (a) the
payment in full in cash of the Guaranteed Obligations and all other amounts
payable under this Guaranty, (b) the Termination Date and (c) the latest date of
expiration or termination of all Letters of Credit, such amount shall be
received and held in trust for the benefit of the Lenders, shall be segregated
from other property and funds of the Guarantor and shall forthwith be paid or
delivered to the Agent in the same form as so received (with any necessary
endorsement or assignment) to be credited and applied to the Guaranteed
Obligations and all other amounts payable under this Guaranty, whether matured
or unmatured, in

                                       4
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accordance with the terms of the Loan Documents to be held as Collateral for any
Guaranteed Obligations or other amounts payable under this Guaranty thereafter
arising. If (i) any Guarantor shall make payment to any Lender of all or any
part of the Guaranteed Obligations, (ii) all of the Guaranteed Obligations and
all other amounts payable under this Guaranty shall have been paid in full in
cash, (iii) the Termination Date shall have occurred and (iv) all Letters of
Credit shall have expired or been terminated, the Lenders will, at the
Guarantor's request and expense, execute and deliver to the Guarantor
appropriate documents, without recourse and without representation or warranty,
necessary to evidence the transfer by subrogation to the Guarantor of an
interest in the Guaranteed Obligations resulting from such payment made by the
Guarantor pursuant to this Guaranty.

     Section 6.  Payments Free and Clear of Taxes, Etc.
                 -------------------------------------

          (a) Any and all payments made by the Guarantor under or in respect of
this Guaranty, or any other Loan Document shall be made, in accordance with
Section 2.09 of the Credit Agreement, free and clear of and without deduction
for any and all present or future Taxes.  If the Guarantor shall be required by
law to deduct any Taxes from or in respect of any sum payable under or in
respect of this Guaranty, or any other Loan Document to any Lender, (i) the sum
payable by the Guarantor shall be increased as may be necessary so that after
the Guarantor and the Agent have made all required deductions (including
deductions applicable to additional sums payable under this Section 5), such
Lender receives an amount equal to the sum it would have received had no such
deductions been made, (ii) the Guarantor shall make all such deductions and
(iii) the Guarantor shall pay the full amount deducted to the relevant taxation
authority or other authority in accordance with applicable law.

          (b) In addition, the Guarantor agrees to pay any present or future
Other Taxes that arise from any payment made by or on behalf of the Guarantor
under or in respect of this Guaranty, or any other Loan Document or from the
execution, delivery or registration of, performance under, or otherwise with
respect to, this Guaranty, and the other Loan Documents.

          (c) The Guarantor will indemnify each Lender for and hold it harmless
against the full amount of Taxes and Other Taxes, and for the full amount of
taxes of any kind imposed by any jurisdiction on amounts payable under this
Section 6, imposed on or paid by such Lender and any liability (including
penalties, additions to tax, interest and expenses) arising therefrom or with
respect thereto.  This indemnification shall be made within 30 days from the
date such Lender makes written demand therefor.

          (d) Within 30 days after the date of any payment of Taxes by or on
behalf of the Guarantor, the Guarantor shall furnish to the Agent, at its
address referred to in Section 9, the original or a certified copy of a receipt
evidencing such payment.  In the case of any payment hereunder by or on behalf
of the Guarantor through an account or branch outside the United States or by or
on behalf of the Guarantor by a payor that is not a United States person, if the
Guarantor determines that no Taxes are payable in respect thereof, the Guarantor
shall furnish, or shall cause such payor to furnish, to the Agent, at such
address, an opinion of counsel acceptable to the Agent stating that such payment
is exempt from Taxes.  For purposes of subsections (d) and (e) of this Section
6, the terms "United States" and "United States person" shall have the meanings
specified in Section 7701 of the Internal Revenue Code.

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<PAGE>

          (e) Upon the reasonable request in writing of the Guarantor, each
Lender organized under the laws of a jurisdiction outside the United States
shall, on or prior to the date of its execution and delivery of the Credit
Agreement in the case of each Initial Lender or Initial Issuing Bank, as the
case may be, and on or prior to the date of the Assignment and Acceptance
pursuant to which it becomes a Lender in the case of each other party, and from
time to time thereafter upon the reasonable request in writing by the Guarantor
(but only so long thereafter as such Lender remains lawfully able to do so),
provide each the Agent and the Guarantor with two original Internal Revenue
Service forms 1001 or 4224, as appropriate, or any successor or other form
prescribed by the Internal Revenue Service, certifying that such Lender is
exempt from or entitled to a reduced rate of United States withholding tax on
payments under the Credit Agreement or the Notes.  If the forms provided by a
Lender at the time such Lender first becomes a party to the Credit Agreement
indicates a United States interest withholding tax rate in excess of zero,
withholding tax at such rate shall be considered excluded from Taxes unless and
until such Lender provides the appropriate form certifying that a lesser rate
applies, whereupon withholding tax at such lesser rate only shall be considered
excluded from Taxes for periods governed by such forms; provided, however, that
if, in the case of a Lender becoming a party to the Credit Agreement, at the
date of the Assignment and Acceptance pursuant to which a Lender becomes a party
to the Credit Agreement, the Lender assignor was entitled to payments under
subsection (a) of this Section 6 in respect of United States withholding tax
with respect to interest paid at such date, then, to such extent, the term Taxes
shall include (in addition to withholding taxes that may be imposed in the
future or other amounts otherwise includable in Taxes) United States withholding
tax, if any, applicable with respect to the Lender assignee on such date.  If
any form or document referred to in this subsection (e) and requested by the
Guarantor pursuant to this subsection (e) requires the disclosure of
information, other than information necessary to compute the tax payable and
information required on the date hereof by Internal Revenue Service form 1001
or 4224 (or the related certificate described above), that the applicable Lender
reasonably considers to be confidential, such Lender shall give notice thereof
to the Guarantor and shall not be obligated to include in such form or document
such confidential information.

          (f) For any period with respect to which a Lender has failed to
provide the Guarantor, following the Guarantor's request therefor pursuant to
subsection (e) above, with the appropriate form described in subsection (e)
above (other than if such failure is due to a change in law occurring after the
       ----------
date on which a form originally was required to be provided or if such form
otherwise is not required under subsection (e) above), such Lender shall not be
entitled to indemnification under subsection (a) or (c) of this Section 6 with
respect to Taxes imposed by the United States by reason of such failure;
provided, however, that should a Lender become subject to Taxes because of its
failure to deliver a form required hereunder, the Guarantor shall take such
steps as such Lender shall reasonably request to assist such Lender to recover
such Taxes.

          (g) If any Lender determines, in its sole discretion, that it has
actually and finally realized, by reason of a refund, deduction or credit of any
Taxes paid or reimbursed by the Guarantor pursuant to subsection (a) or (c)
above in respect of payments under the Loan Documents, a current monetary
benefit that it would otherwise not have obtained, and that would result in the
total payments under this Section 6 exceeding the amount needed to make such
Lender whole, such Lender shall pay to the Guarantor, with reasonable promptness
following the

                                       6
<PAGE>

date on which it actually realizes such benefit, an amount equal to the lesser
of the amount of such benefit or the amount of such excess, in each case net of
all out-of-pocket expenses in securing such refund, deduction or credit.

     Section 7.  Representations and Warranties.  The Guarantor hereby makes
                 ------------------------------
each representation and warranty made in the Loan Documents by the Borrower with
respect to the Guarantor and the Guarantor hereby further represents and
warrants as follows:

          (a) There are no conditions precedent to the effectiveness of this
     Guaranty that have not been satisfied or waived.

          (b) The Guarantor has, independently and without reliance upon any
     Lender and based on such documents and information as it has deemed
     appropriate, made its own credit analysis and decision to enter into this
     Guaranty and each other Loan Document to which it is or is to be a party,
     and the Guarantor has established adequate means of obtaining from each
     other Loan Party on a continuing basis information pertaining to, and is
     now and on a continuing basis will be completely familiar with, the
     business, condition (financial or otherwise), operations, performance,
     properties and prospects of such other Loan Party.

          (c) The Guarantor and each of its Subsidiaries is a corporation duly
     organized, validly existing and in good standing under the laws of the
     jurisdiction of its organization.

          (d) The execution, delivery and performance by the Guarantor of the
     Loan Documents to which it is or is to be a party, and the consummation of
     the transactions contemplated thereby, are within the Guarantor's corporate
     powers, have been duly authorized by all necessary corporate action, and do
     not contravene (i) the Guarantor's charter or by-laws or (ii) law or any
     contractual restriction binding on or affecting the Guarantor.

          (e) No authorization or approval or other action by, and no notice to
     or filing with, any governmental authority or regulatory body or any other
     third party is required for the due execution, delivery and performance by
     the Guarantor of the Loan Documents to which it is or is to be a party.

          (f) The Guarantor and its Subsidiaries own all of the assets reflected
     in the Consolidated balance sheet of the Guarantor as at the date of such
     balance sheet or acquired since that date (except property and assets sold
     or otherwise disposed of in accordance with the provisions of the Credit
     Agreement since that date).

     Section 8.  Covenants.  The Guarantor covenants and agrees that, so long
                 ---------
as any part of the Guaranteed Obligations shall remain unpaid, any Letter of
Credit shall be outstanding, any Lender shall have any Commitment, the Guarantor
will perform and observe, and cause each of its Subsidiaries to perform and
observe, all of the terms, covenants and agreements set forth in the Loan
Documents on its or their part to be performed or observed or that the Borrower
has agreed to cause the Guarantor or the Subsidiaries to perform or observe.

                                       7
<PAGE>

     Section 9.  Amendments, Etc.    (a) No amendment or waiver of any provision
                 ---------------
of this Guaranty and no consent to any departure by the Guarantor therefrom
shall in any event be effective unless the same shall be in writing and signed
by the Agent and the Required Lenders, and then such waiver or consent shall be
effective only in the specific instance and for the specific purpose for which
given; provided, however, that no amendment, waiver or consent shall, unless in
writing and signed by all of the Lenders, (i) reduce or limit the obligations of
the Guarantor hereunder, release the Guarantor hereunder or otherwise limit the
Guarantor's liability with respect to the Obligations owing to the Lenders under
or in respect of the Loan Documents except as provided in the next succeeding
sentence, (ii) postpone any date fixed for payment hereunder or (c) change the
number of Lenders or the percentage of (x) the Commitments, (y) the aggregate
unpaid principal amount of the Advances or (z) the aggregate Available Amount of
outstanding Letters of Credit that, in each case, shall be required for the
Lenders or any of them to take any action hereunder.

     Section 10.  Notices, Etc.    All notices and other communications provided
                  ------------
for hereunder shall be in writing (including telegraphic, telecopy or telex
communication) and mailed, telegraphed, telecopied, telexed or delivered to it,
if to the Guarantor, addressed to it in care of the Borrower at the Borrower's
address specified in Section 9.02 of the Credit Agreement, if to any Agent or
any Lender Party, at its address specified in Section 9.02 of the Credit
Agreement or, as to any party, at such other address as shall be designated by
such party in a written notice to each other party.  All such notices and other
communications shall, when mailed, telegraphed, telecopied or telexed, be
effective when deposited in the mails, delivered to the telegraph company,
transmitted by telecopier or confirmed by telex answerback, respectively.
Delivery by telecopier of an executed counterpart of a signature page to any
amendment or waiver of any provision of this Guaranty or of any Guaranty
Supplement to be executed and delivered hereunder shall be effective as delivery
of an original executed counterpart thereof.

     Section 11.  No Waiver, Remedies.  No failure on the part of any Lender
                  -------------------
to exercise, and no delay in exercising, any right hereunder shall operate as a
waiver thereof; nor shall any single or partial exercise of any right hereunder
preclude any other or further exercise thereof or the exercise of any other
right.  The remedies herein provided are cumulative and not exclusive of any
remedies provided by law.

     Section 12.  Right of Set-off.  Upon (a) the occurrence and during the
                  ----------------
continuance of any Event of Default and (b) the making of the request or the
granting of the consent specified by Section 7.01 of the Credit Agreement to
authorize the Agent to declare the Notes due and payable pursuant to the
provisions of said Section 7.01, each Agent and each Lender and each of their
respective Affiliates is hereby authorized at any time and from time to time, to
the fullest extent permitted by law, to set off and apply any and all deposits
(general or special, time or demand, provisional or final) at any time held and
other indebtedness at any time owing by such, Agent, Lender or such Affiliate to
or for the credit or the account of the Guarantor against any and all of the
Obligations of the Guarantor now or hereafter existing under the Loan Documents,
irrespective of whether such Agent or such Lender shall have made any demand
under this Guaranty or any other Loan Document and although such Obligations may
be unmatured.  Each Agent and each Lender agrees promptly to notify the
Guarantor after any such set-off and application; provided, however, that the
failure to give such notice shall not affect the validity of such set-off and
application.  The rights of each Agent, Lender and their respective Affiliates

                                       8
<PAGE>

under this Section are in addition to other rights and remedies (including,
without limitation, other rights of set-off) that such Agent, such Lender and
their respective Affiliates may have.

     Section 13.  Indemnification.
                  ---------------

          (a) Without limitation on any other Obligations of the Guarantor or
remedies of the Lenders under this Guaranty, the Guarantor shall, to the fullest
extent permitted by law, indemnify, defend and save and hold harmless each
Lender and each of their Affiliates and their respective officers, directors,
employees, agents and advisors (each, an "Indemnified Party") from and against,
and shall pay on demand, any and all claims, damages, losses, liabilities and
expenses (including, without limitation, reasonable fees and expenses of
counsel) that may be incurred by or asserted or awarded against any Indemnified
Party in connection with or as a result of any failure of any Guaranteed
Obligations to be the legal, valid and binding obligations of any Loan Party
enforceable against such Loan Party in accordance with their terms.

          (b) The Guarantor hereby also agrees that none of the Indemnified
Parties shall have any liability (whether direct or indirect, in contract, tort
or otherwise) to the Guarantor or any of its Affiliates or any of their
respective officers, directors, employees, agents and advisors, and the
Guarantor hereby agrees not to assert any claim against any Indemnified Party on
any theory of liability, for special, indirect, consequential or punitive
damages arising out of or otherwise relating to the Facilities, the actual or
proposed use of the proceeds of the Advances or the Letters of Credit, the Loan
Documents or any of the transactions contemplated by the Loan Documents.

          (c) Without prejudice to the survival of any of the other agreements
of the Guarantor under this Guaranty or any of the other Loan Documents the
agreements and obligations of the Guarantor contained in Section I(a) (with
respect to enforcement expenses), the last sentence of Section 3, Section 6 and
this Section 13 shall survive the payment in full of the Guaranteed Obligations
and all of the other amounts payable under this Guaranty.

     Section 14.  Subordination.  The Guarantor hereby subordinates any and
                  -------------
all debts, liabilities and other Obligations owed to the Guarantor by each other
Loan Party (the "Subordinated Obligations") to the Guaranteed Obligations to the
extent and in the manner hereinafter set forth in this Section 14:

          (a) Prohibited Payments, Etc.  Except during the continuance of a
              ------------------------
     Default (including the commencement and continuation of any proceeding
     under any Bankruptcy Law relating to any other Loan Party), the Guarantor
     may receive regularly scheduled payments from any other Loan Party on
     account of the Subordinated Obligations.  After the occurrence and during
     the continuance of any Default (including the commencement and continuation
     of any proceeding under any Bankruptcy Law relating to any other Loan
     Party), however, unless the Agent otherwise agrees, the Guarantor shall not
     demand, accept or take any action to collect any payment on account of the
     Subordinated Obligations.

          (b) Prior Payment of Guaranteed Obligations.  In any proceeding under
              ---------------------------------------
     any Bankruptcy Law relating to any other Loan Party, the Guarantor agrees
     that the Lenders

                                       9
<PAGE>

     shall be entitled to receive payment in full in cash of all Guaranteed
     Obligations (including all interest and expenses accruing after the
     commencement of a proceeding under any Bankruptcy Law, whether or not
     constituting an allowed claim in such proceeding ("Post Petition
     Interest")) before the Guarantor receives payment of any Subordinated
     Obligations.

          (c) Turn-Over.  After the occurrence and during the continuance of any
              ---------
     Default (including the commencement and continuation of any proceeding
     under any Bankruptcy Law relating to any other Loan Party), the Guarantor
     shall, if the Agent so requests, collect, enforce and receive payments on
     account of the Subordinated Obligations as trustee for the Lenders and
     deliver such payments to the Agent on account of the Guaranteed Obligations
     (including all Post Petition Interest), together with any necessary
     endorsements or other instruments of transfer, but without reducing or
     affecting in any manner the liability of the Guarantor under the other
     provisions of this Guaranty.

          (d) Agent Authorization.  After the occurrence and during the
              -------------------
     continuance of any Default (including the commencement and continuation of
     any proceeding under any Bankruptcy Law relating to any other Loan Party),
     the Agent is authorized and empowered (but without any obligation to so
     do), in its discretion, (i) in the name of each Guarantor, to collect and
     enforce, and to submit claims in respect of, Subordinated Obligations and
     to apply any amounts received thereon to the Guaranteed Obligations
     (including any and all Post Petition Interest), and (ii) to require the
     Guarantor (A) to collect and enforce, and to submit claims in respect of,
     Subordinated Obligations and (B) to pay any amounts received on such
     obligations to the Agent for application to the Guaranteed Obligations
     (including any and all Post Petition Interest).

     Section 15.  Continuing Guaranty; Assignments under the Credit Agreement.
                  -----------------------------------------------------------
This Guaranty is a continuing guaranty and, subject to the provisions of
Section 2, shall (a) remain in full force and effect until the latest of (i) the
payment in full in cash of the Guaranteed Obligations and all other amounts
payable under this Guaranty, (ii) the Termination Date and (iii) the date of
expiration or termination of all Letters of Credit, (b) be binding upon the
Guarantor, its successors and assigns and (c) inure to the benefit of and be
enforceable by the Lenders and their successors, transferees and assigns.
Without limiting the generality of clause (c) of the immediately preceding
sentence, any Lender may assign or otherwise transfer all or any portion of its
rights and obligations under the Credit Agreement (including, without
limitation, all or any portion of its Commitments, the Advances owing to it and
the Note or Notes held by it) to any other Person, and such other Person shall
thereupon become vested with all the benefits in respect thereof granted to such
Lender herein or otherwise, in each case as and to the extent provided in
Section 9.07 of the Credit Agreement.  The Guarantor shall not assign its rights
hereunder or any interest herein without the prior written consent of the
Lenders.

     Section 16.  Execution in Counterparts.  This Guaranty and each
                  -------------------------
amendment, waiver and consent with respect hereto may be executed in any number
of counterparts and by different parties thereto in separate counterparts, each
of which when so executed shall be deemed to be an original and all of which
taken together shall constitute one and the same agreement.

                                       10
<PAGE>

Delivery of an executed counterpart of a signature page to this Guaranty by
telecopier shall be effective as delivery of an original executed counterpart of
this Guaranty.

     Section 17.  Governing Law; Jurisdiction; Waiver of Jury Trial, Etc.
                  ------------------------------------------------------

          (a) This Guaranty shall be governed by, and construed in accordance
with, the laws of the State of New York.

          (b) The Guarantor hereby irrevocably and unconditionally submits, for
itself and its property, to the nonexclusive jurisdiction of any New York State
court or federal court of the United States of America sitting in New York City,
and any appellate court from any thereof, in any action or proceeding arising
out of or relating to this Guaranty, or any of the other Loan Documents to which
it is or is to be a party, or for recognition or enforcement of any judgment,
and the Guarantor hereby irrevocably and unconditionally agrees that all claims
in respect of any such action or proceeding may be heard and determined in any
such New York State court or, to the extent permitted by law, in such federal
court.  The Guarantor agrees that a final judgment in any such action or
proceeding shall be conclusive and may be enforced in other jurisdictions by
suit on the judgment or in any other manner provided by law.  Nothing in this
Guaranty or any other Loan Document shall affect any right that any party may
otherwise have to bring any action or proceeding relating to this Guaranty or
any other Loan Document in the courts of any jurisdiction.

          (c) The Guarantor irrevocably and unconditionally waives, to the
fullest extent it may legally and effectively do so, any objection that it may
now or hereafter have to the laying of venue of any suit, action or proceeding
arising out of or relating to this Guaranty or any of the other Loan Documents
to which it is or is to be a party in any New York State or federal court.  The
Guarantor hereby irrevocably waives, to the fullest extent permitted by law, the
defense of an inconvenient forum to the maintenance of such suit, action or
proceeding in any such court.

          (d) THE GUARANTOR HEREBY IRREVOCABLY WAIVES ALL RIGHT TO TRIAL BY JURY
IN ANY ACTION, PROCEEDING OR COUNTERCLAIM (WHETHER BASED ON CONTRACT, TORT OR
OTHERWISE) ARISING OUT OF OR RELATING TO ANY OF THE LOAN DOCUMENTS, THE ADVANCES
OR THE ACTIONS OF ANY LENDER IN THE NEGOTIATION, ADMINISTRATION, PERFORMANCE OR
ENFORCEMENT THEREOF.

                                       11
<PAGE>

     IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be duly
executed and delivered by its officer thereunto duly authorized as of the date
first above written.

                              c-quential, Inc., a Delaware corporation,

                              By: /s/ John F. Burns
                                  -------------------------------------
                                  Title:

                                       12<PAGE>

                                                                   EXHIBIT 10.20

                             ARTHUR D. LITTLE, INC.
                             ----------------------
                                   Acorn Park
                            Cambridge, MA 02140-2390

                               SECURITY AGREEMENT
                               ------------------

     SECURITY AGREEMENT, dated as of April 25, 2000 (this "Agreement"), among
Arthur D. Little, Inc., a Massachusetts corporation ("ADL"), Arthur D. Little
International, Inc., a Massachusetts corporation ("ADL International"), and all
the subsidiaries of ADL and ADL International listed on Annex A attached hereto
("Subsidiaries") (ADL, ADL International and each such Subsidiary being
individually referred to herein as a "Company" and collectively as the
"Companies"), and Citicorp USA, Inc., as collateral agent (hereinafter, in such
capacity, the "Collateral Agent") for: (i) Citibank, N.A., The Chase Manhattan
Bank and other banking institutions (hereinafter, collectively, the "Banks")
which are or may become parties to that certain Amended and Restated Credit
Agreement dated as of April 25, 2000 (as amended and in effect from time to
time, the "Credit Agreement"), among ADL, ADL International, Citibank, N.A., as
agent and the Banks; and (ii) the holders from time to time (individually, a
"Noteholder," and collectively, the "Noteholders") of those certain Adjustable
Rate Amended and Restated Senior Secured Notes, in the aggregate principal
amount of $35,000,000 (as amended from time to time, the "Notes") issued by ADL
pursuant to that certain Amended and Restated Note Purchase Agreement dated as
of April 25, 2000 (as amended from time to time, the "Note Purchase Agreement"),
among ADL and the Noteholders.

     WHEREAS, the Banks and the Noteholders are parties to that certain
Collateral Agency and Intercreditor Agreement (the "Intercreditor Agreement")
dated as of April 25, 2000;

     WHEREAS, it is a condition precedent to the Banks' entering into the Credit
Agreement or making any loans or otherwise extending credit to ADL or ADL
International under the Credit Agreement, and accepting the promissory note to
be issued by ADL and ADL International under the Credit Agreement (the "Credit
Note"), that each of Companies execute and deliver to the Collateral Agent, for
the benefit of the Banks and the Noteholders, a security agreement in
substantially the form hereof,

     WHEREAS, it is a condition precedent to the Noteholders' entering into the
Note Purchase Agreement that ADL International, and c-quential, Inc., a Delaware
corporation ("c-quential") guaranty the payment in full of the Notes (the
"Guaranty");

     WHEREAS, it is a condition precedent to the Banks entering into the Credit
Agreement that c-quential guaranty in full the obligations of the Companies
thereunder (the "TIME Guaranty");

     WHEREAS, it is a condition precedent to the Noteholders' entering into the
Note Purchase Agreement that each of the Companies execute and deliver to the
Collateral Agent, for the benefit of the Banks and the Noteholders, a security
agreement in substantially the form hereof,
<PAGE>

     WHEREAS, each of the Companies wishes to grant security interests in favor
of the Collateral Agent, for the equal and ratable benefit of the Banks and the
Noteholders, as herein provided; and

     NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

     1.  Definitions. All terms defined in the Uniform Commercial Code of the
State of New York "UCC") and used herein but not defined shall have the same
meaning herein as specified in the UCC; provided, however, that the term
                                        ------------------
"instrument" shall be such term as defined in Article 9 of the UCC of such
jurisdiction rather than Article 3.

     2.  Grant of Security Interest.

          2.1.  Collateral Granted. Each of the Companies hereby grants to the
                ------------------
Collateral Agent, for the benefit of the Banks and the Noteholders, to secure
the payment and performance in full of all of the obligations of ADL, ADL
International and c-quential under (i) the Note Purchase Agreement, the Notes
and the Guaranty (the "Senior Note Indebtedness"), and (ii) the Credit
Agreement, Credit Note and the TIME Guaranty (the "Bank Lender Indebtedness"
and, together with the Senior Note Indebtedness, the "Secured Obligations"), a
security interest in the following properties, assets and rights of such
Company, wherever located, whether now owned or hereafter acquired or arising
(all of the same being hereinafter called the "Collateral"):

               (a) any and all rights to the payment of money or other forms of
     consideration of any kind (whether classified under the Uniform Commercial
     Code as accounts, contract rights, chattel paper, general intangibles, or
     otherwise) arising from goods sold or services rendered, including accounts
     receivable, letters of credit and the right to receive payment thereunder,
     chattel paper, insurance proceeds, contract rights (being any rights under
     contracts not yet earned by performance and not evidenced by an instrument
     or chattel paper, which contracts relate to or arise out of any of the
     Collateral), notes, drafts, instruments, documents, acceptances, and all
     other debts, obligations and liabilities in whatever form from any person;

               (b) all guarantees, security, liens, pledges, charges,
     conditional sale or other title retention agreements, or other security
     interests, security titles or encumbrances of any kind in respect of any
     such right to the payment of money;

               (c) all documents and instruments evidencing or pertaining to any
     item of Collateral;

               (d) all files, correspondence, computer programs, tapes, discs
     and related data processing software which contain information identifying
     or pertaining to any of the Collateral, or showing the amounts thereof or
     payments thereon or otherwise necessary or helpful in the realization
     thereon or the collection thereof, and

               (e) any and all products and proceeds of the foregoing.

                                       2
<PAGE>

     3.  Title to Collateral. Each Company is the owner of the Collateral
         -------------------
purported to be owned by it, free from any adverse lien, security interest or
other encumbrance, except for the security interest created by this Agreement.

     4.  Continuous Perfection. Each Company's principal place of business or,
         ---------------------
if more than one, chief executive office is indicated on the Perfection
Certificate delivered to the Collateral Agent herewith with respect to such
Company (the "Perfection Certificate"). No Company will change the same, or its
name, identity or corporate structure in any manner, without providing at least
30 days prior written notice to the Collateral Agent. Each Company will maintain
the books and records relating to its Collateral at those locations listed on
its Perfection Certificate, and no Company will remove the Collateral from such
locations without providing at least 30 days prior written notice to the
Collateral Agent.

     5.  No Liens. Except for the security interest herein granted, each Company
         --------
is the owner of its Collateral free from any lien, security interest or other
encumbrance, and such Company shall defend the same against all claims and
demands of all persons at any time claiming the same or any interests therein
adverse to the Collateral Agent, the Noteholders or any of the Banks. No Company
shall pledge, mortgage, create, or suffer to exist a security interest in its
Collateral in favor of any person or entity other than the Collateral Agent.

     6.  No Transfers. No Company will sell or otherwise transfer any of its
         ------------
Collateral or any interest therein, other than (i) in the ordinary course of
business and (ii) transfers to c-quential and its subsidiaries of Collateral
consisting of and relating to obligations of the account debtors listed on
Schedule I hereto and such other account debtors as shall have been approved in
writing by the Collateral Agent. Collateral sold or otherwise transferred in
compliance with this (S)6 shall be free of the security interest created by this
Agreement.

     7. Inspection of Collateral: Compliance with Law. The Collateral Agent or
        ---------------------------------------------
its designee may inspect any and all books, records, ledger cards, computer
programs, computer disks and tapes and other similar property and general
intangibles at any time evidencing or relating to the Collateral, at any
reasonable time and wherever located.

     8. Collateral Protection Expenses; Preservation of Collateral.
        ----------------------------------------------------------

               8.1.  Expenses Incurred by Collateral Agent. In its discretion,
                     -------------------------------------
     the Collateral Agent may discharge taxes and other encumbrances at any time
     levied or placed on any of the Collateral and pay any necessary filing
     fees. The Companies agree to reimburse the Collateral Agent on demand for
     any and all expenditures so made. The Collateral Agent shall have no
     obligation to any Company to make any such expenditure, nor shall the
     making thereof relieve any Company of any default.

               8.2.  Collateral Agent's Obligations and Duties. Anything herein
                     -----------------------------------------
     to the contrary notwithstanding, each Company shall remain liable under
     each contract or agreement contained in the Collateral. Neither the
     Collateral Agent nor any Noteholder or Bank shall have any obligation or
     liability under any such contract or agreement by reason of or arising out
     of this Agreement or the receipt by the Collateral Agent, any Noteholder or
     Bank of any payment relating to any of the Collateral. Neither the
     Collateral Agent, nor any Noteholder or Bank shall be obligated in any
     manner to

                                       3
<PAGE>

     perform any of the obligations of any Company under or pursuant to any
     contract or agreement, to make inquiry as to the nature or sufficiency of
     any payment received in respect of the Collateral or as to the sufficiency
     of any performance by any party under any such contract or agreement, to
     present or file any claim, to take any action to enforce any performance or
     to collect the payment of any amounts which may have been assigned to the
     Collateral Agent or to which the Collateral Agent, any Noteholder or Bank
     may be entitled at any time or times. The Collateral Agent's sole duty with
     respect to the custody, safe keeping and physical preservation of the
     Collateral in its possession, under (S)9207 of the Uniform Commercial Code
     of the State of New York or otherwise, shall be to deal with such
     Collateral in the same manner as the Collateral Agent deals with similar
     property for its own account.

     9.  Notification to Account Debtors and Other Obligors. If an Event of
         --------------------------------------------------
Default shall exist under (and as defined in) the Note Purchase Agreement or the
Credit Agreement, each Company shall, at the request of the Collateral Agent,
notify account debtors on accounts, chattel paper and general intangibles of
such Company, and obligors on instruments for which such Company is an obligee,
of the security interest of the Collateral Agent, and that payment thereof is to
be made directly to the Collateral Agent; and the Collateral Agent may itself,
if any such Event of Default shall exist, without notice to or demand upon such
Company, so notify such account debtors and obligors. After the making of such a
request or the giving of any such notification, each Company shall hold any
proceeds of collection of accounts, chattel paper, general intangibles and
instruments received by such Company as trustee for the Collateral Agent, for
the benefit of the Noteholders and the Banks, without commingling the same with
other funds, and shall turn the same over to the Collateral Agent in the
identical form received, together with any necessary endorsements or
assignments. The Collateral Agent shall apply the proceeds of collection of
accounts, chattel paper, general intangibles and instruments received by the
Collateral Agent to the Secured Obligations in the order set forth in the
Intercreditor Agreement, such proceeds to be immediately entered after final
payment in cash or solvent credits of the items giving rise to them.

     10.  Further Assurances. Each Company, at its own expense, shall do, make,
          ------------------
execute and deliver all such additional and further acts, things, deeds,
assurances and instruments as the Collateral Agent may require more completely
to vest in, perfect and assure to the Collateral Agent, the Noteholders and the
Banks their respective rights hereunder or in any of the Collateral.

     11.  Power of Attorney.
          -----------------

          11.1.  Appointment and Powers of Collateral Agent. Each Company hereby
                 ------------------------------------------
irrevocably constitutes and appoints the Collateral Agent and any officer or
agent thereof, with full power of substitution, as its true and lawful attorneys
- in- fact with full irrevocable power and authority in the place and stead of
such Company or in the Collateral Agent's own name, for the purpose of carrying
out the terms of this Agreement, to take any and all appropriate action and to
execute any and all documents and instruments that may be necessary or desirable
to accomplish the purposes of this Agreement and, without limiting the
generality of the foregoing, hereby gives said attorneys the power and right, on
behalf of such Company, without notice to or assent by such Company, to do the
following:

                                       4
<PAGE>

               (a) upon the occurrence and during the continuance of an Event of
     Default under (and as defined in) the Note Purchase Agreement or the Credit
     Agreement, generally to sell, transfer, pledge, make any agreement with
     respect to or otherwise deal with any of the Collateral in such manner as
     is consistent with the Uniform Commercial Code of the State of New York and
     as fully and completely as though the Collateral Agent were the absolute
     owner thereof for all purposes, and to do at such Company's expense, at any
     time, or from time to time, all acts and things which the Collateral Agent
     deems necessary to protect, preserve or realize upon the Collateral and the
     Collateral Agent's security interest therein, in order to effect the intent
     of this Agreement, all as fully and effectively as such Company might do;
     and

               (b) to file such financing statements with respect hereto, with
     or without such Company's signature, or a photocopy of this Agreement in
     substitution for a financing statement, as the Collateral Agent may deem
     appropriate and to execute in such Company's name such financing statements
     and amendments thereto and continuation statements which may require such
     Company's signature.

          11.2.  Ratification by Company. To the extent permitted by law, each
                 -----------------------
Company hereby ratifies all that said attorneys shall lawfully do or cause to be
done by virtue hereof. This power of attorney is a power coupled with an
interest and shall be irrevocable.

          11.3.  No Duty on Collateral Agent. The powers conferred on the
                 ---------------------------
Collateral Agent hereunder are solely to protect the interests of the Collateral
Agent, the Noteholders and the Banks in the Collateral and shall not impose any
duty upon the Collateral Agent to exercise any such powers. The Collateral Agent
shall be accountable only for the amounts that it actually receives as a result
of the exercise of such powers and neither it nor any of its officers,
directors, employees or agents shall be responsible to any Company for any act
or failure to act, except for the Collateral Agent's own gross negligence or
willful misconduct.

     12.  Remedies. If an Event of Default shall exist under (and as defined in)
          --------
either the Credit Agreement or the Note Purchase Agreement, the Collateral Agent
may, without notice to or demand upon any Company, declare this Agreement to be
in default, and the Collateral Agent shall thereafter have in any jurisdiction
in which enforcement hereof is sought, in addition to all other rights and
remedies, the rights and remedies of a secured party under the Uniform
Commercial Code. Unless the Collateral is perishable or threatens to decline
speedily in value or is of a type customarily sold on a recognized market, the
Collateral Agent shall give to the relevant Company at least ten business days
prior written notice of the time and place of any public sale of its Collateral
or of the time after which any private sale or any other intended disposition is
to be made. The Companies hereby acknowledge that ten business days prior
written notice of such sale or sales shall be reasonable notice. In addition,
each Company waives any and an rights that it may have to a judicial hearing in
advance of the enforcement of any of the Collateral Agent's rights hereunder,
including, without limitation, its right following an Event of Default to take
immediate possession of the Collateral and to exercise its rights with respect
thereto.

     13.  No Waiver, etc. Each Company waives demand, notice, protest, notice of
          --------------
acceptance of this Agreement, notice of loans made, credit extended, Collateral
received or

                                       5
<PAGE>

delivered or other action taken in reliance hereon and all other demands and
notices of any description. With respect to both the Secured Obligations and the
Collateral, each Company assents to any extension or postponement of the time of
payment or any other indulgence, to any substitution, exchange or release of or
failure to perfect any security interest in any Collateral, to the addition or
release of any party or person primarily or secondarily liable, to the
acceptance of partial payment thereon and the settlement, compromising or
adjusting of any thereof, all in such manner and at such time or times as the
Collateral Agent may deem advisable. The Collateral Agent shall have no duty as
to the collection or protection of the Collateral or any income thereon, nor as
to the preservation of rights against prior parties, nor as to the preservation
of any rights pertaining thereto beyond the safe custody thereof as set forth in
(S)8.2. The Collateral Agent shall not be deemed to have waived any of its
rights upon or under the Secured Obligations or the Collateral unless such
waiver shall be in writing and signed by the Collateral Agent. No delay or
omission on the part of the Collateral Agent in exercising any right shall
operate as a waiver of such right or any other right. A waiver on any one
occasion shall not be construed as a bar to or waiver of any right on any future
occasion. All rights and remedies of the Collateral Agent with respect to the
Secured Obligations or the Collateral, whether evidenced hereby or by any other
instrument or papers, shall be cumulative and may be exercised singularly,
alternatively, successively or concurrently at such time or at such times as the
Collateral Agent deems expedient, provided, however, that the exercise of such
                                  --------  -------
rights and remedies shall be in accordance with the Intercreditor Agreement.

     14.  Marshalling. Neither the Collateral Agent nor any Noteholder nor any
          -----------
Bank shall be required to marshal any present or future collateral security
(including but not limited to this Agreement and the Collateral) for, or other
assurances of payment of, the Secured Obligations or any of them or to resort to
such collateral security or other assurances of payment in any particular order,
and all of the rights of the Collateral Agent hereunder and of the Collateral
Agent, the Noteholders or the Banks in respect of such collateral security and
other assurances of payment shall be cumulative and in addition to all other
rights, however existing or arising. To the extent that it lawfully may, each
Company hereby agrees that it will not invoke any law relating to the
marshalling of collateral which might cause delay in or impede the enforcement
of the Collateral Agent's rights under this Agreement or under any other
instrument creating or evidencing any of the Secured Obligations or under which
any of the Secured Obligations is outstanding or by which any of the Secured
Obligations is secured or payment thereof is otherwise assured, and, to the
extent that it lawfully may, each Company hereby irrevocably waives the benefits
of all such laws.

     15.  Indemnity. Each Company shall indemnify, defend, save and hold
          ---------
harmless each of the Collateral Agent, Banks, Noteholders and each of their
Affiliates and their respective officers, directors, employees, agents and
advisors (each, an "Indemnified Party") from and against, and shall pay on
demand, any and all claims, damages, losses, liabilities and expenses
(including, without limitation, reasonable fees and expenses of counsel) that
may be incurred by or asserted or awarded against any Indemnified Party, in each
case arising out of or in connection with or resulting from this Agreement
(including, without limitation, enforcement of this Agreement), except to the
extent such claim, damage, loss, liability or expense is found in a final, non-
appealable judgment by a court of competent jurisdiction to have resulted from
such Indemnified Party's gross negligence or willful misconduct.

                                       6
<PAGE>

     16.  Proceeds of Dispositions; Expenses. Each Company shall pay to the
          ----------------------------------
Collateral Agent on demand any and all expenses, including reasonable attorneys'
fees and disbursements, incurred or paid by the Collateral Agent in (i) the
administration of this Agreement, (ii) the custody, preservation, use or
operation of, or the sale of, collection from or other realization upon, any of
the Collateral of such Company, (iii) the exercise or enforcement of any of the
rights of the Collateral Agent, the Noteholders or the Banks hereunder or (iv)
the failure by such Company to perform or observe any of the provisions hereof.
After deducting all of said expenses, the residue of any proceeds of collection
or sale of the Secured Obligations or Collateral shall, to the extent actually
received in cash, be applied to the payment of the Secured Obligations in such
order or preference as is provided in the Intercreditor Agreement. Upon the
final payment and satisfaction in full of all of the Secured Obligations and
after making any payments required by Section 9-504(l)(c) of the Uniform
Commercial Code of the State of New York, any excess shall be returned to the
Companies.

     17.  Overdue Amounts. Until paid, all amounts due and payable hereunder
          ---------------
shall be a debt secured by the Collateral and shall bear, whether before or
after judgment, interest at the rate of 12% per annum.

     18.  Governing Law; Consent to Jurisdiction. THIS AGREEMENT IS INTENDED TO
          --------------------------------------
TAKE EFFECT AS A SEALED INSTRUMENT AND SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK. Each Company agrees that any
suit for the enforcement of this Agreement may be brought in the courts of the
State of New York or any federal court sitting therein and consents to the non-
exclusive jurisdiction of such court and to service of process in any such suit
being made upon such Company by mail at the address set forth in (S)20. Each
Company hereby waives any objection that it may now or hereafter have to the
venue of any such suit or any such court or that such suit is brought in an
inconvenient court.

     19.  Waiver of Jury Trial. EACH COMPANY WAIVES ITS RIGHT TO A JURY TRIAL
          --------------------
WITH RESPECT TO ANY ACTION OR CLAIM ARISING OUT OF ANY DISPUTE IN CONNECTION
WITH THIS AGREEMENT, ANY RIGHTS OR OBLIGATIONS HEREUNDER OR THE PERFORMANCE OF
ANY SUCH RIGHTS OR OBLIGATIONS. Except as prohibited by law, each Company waives
any right which it may have to claim or recover in any litigation referred to in
the preceding sentence any special, exemplary, punitive. or consequential
damages or any damages other than, or in addition to, actual damages. Each
Company (i) certifies that neither the Collateral Agent, any Noteholder or Bank
nor any representative, agent or attorney of the Collateral Agent, any
Noteholder or Bank has represented, expressly or otherwise, that the Collateral
Agent, any Noteholder or Bank would not, in the event of litigation, seek to
enforce the foregoing waivers and (ii) acknowledges that, in entering into the
Note Purchase Agreement and the Credit Agreement, the Collateral Agent, the
Noteholders and the Banks are relying upon, among other things, the waivers and
certifications contained in this (S)19.

     20.  Notices. All notices and communications provided for hereunder shall
          -------
be in writing and sent (a) by telecopy if the sender on the same day sends a
confirming copy of such notice by a recognized overnight delivery service
(charges prepaid), or (b) by registered or

                                       7
<PAGE>

certified mail with return receipt requested (postage prepaid), or (c) by a
recognized overnight delivery service (with charges prepaid). Any such notice
must be sent:

          (i) if to the Collateral Agent, to it or such nominee at the address
     set forth below, or at such other address as it or such nominee shall have
     specified to the Company in writing in accordance with this (S)20,

               Citicorp USA, Inc.
               399 Park Avenue
               New York, NY 10043
               Attention: New York
               Region Department
               Fax No.: (212) 793-0642

          (ii) if to any of the Companies, to ADL at the address set forth
     below, or at such other address as ADL shall have specified to the
     Collateral Agent in writing in accordance with this (S)20.

               Arthur D. Little, Inc.
               Acorn Park
               Cambridge, MA 02140-2390
               Attention: Chief Financial Officer
               Fax No.: (617) 498-7117

     Notices under this (S)20 will be deemed given only when actually received.

      21. Concerning Revised Article 9 of the Uniform Commercial Code. The
          -----------------------------------------------------------
parties acknowledge and agree to the following provisions of this Agreement in
anticipation of the possible application, in one or more jurisdictions to the
transactions contemplated hereby, of the revised Article 9 of the Uniform
Commercial Code in the form or substantially in the form approved by the
American Law Institute and the National Conference of Commissioners on Uniform
State Law and contained in the 1999 official text of Revised Article 9 ("Revised
Article 9").

            21.1. Attachment. In applying the law of any jurisdiction in which
                  ----------
      Revised Article 9 is in effect, the Collateral shall include, without
      limitation, the following categories of assets as defined in Revised
      Article 9: instruments (including promissory notes), documents, accounts
      (including health-care-insurance receivables), chattel paper (whether
      tangible or electronic), letter-of-credit rights (whether or not the
      letter of credit is evidenced by a writing), commercial tort claims,
      general intangibles (including payment intangibles and software),
      supporting obligations and any and all proceeds of any thereof, wherever
      located, whether now owned and hereafter acquired to the extent arising
      from the sale of goods or the performance of services.

            21.2. Perfection by Filing. The Collateral Agent may at any time and
                  --------------------
      from time to time, pursuant to the provisions of (S)11, file financing
      statements, continuation statements and amendments thereto which contain
      information required by Part 5 of

                                       8
<PAGE>

      Revised Article 9 for the sufficiency or filing office acceptance of any
      financing statement, continuation statement or amendment, including
      whether a Company is an organization, the type of organization and any
      organization identification number issued to a Company. Each Company
      agrees to furnish any such information to the Collateral Agent promptly
      upon request. Any such financing statements, continuation statements or
      amendments may be signed by the Collateral Agent on behalf of any Company,
      as provided in (S)11, and may be filed at any time in any jurisdiction
      whether or not Revised Article 9 is then in effect in that jurisdiction.

            21.3. Other Provisions. In applying the law of any jurisdiction in
      which Revised Article 9 is in effect, the following references to sections
      in this Agreement to existing Article 9 of that, jurisdiction shall be to
      the Revised Article 9 Section of that jurisdiction indicated below:

<TABLE>
<CAPTION>

       Agreement Section           Existing Article 9                 Revised Article 9
<S>                            <C>                               <C>
       3                       (S) 9-103(3)                       Rev. (S) 9-102(a)(34)
       8.2                     (S) 9-207                          Rev. (S) 9-207
       12                      (S)(S) 8-106 and 9-115 (1994)      Rev. (S)(S) 8-106 and 9-106
       16                      (S) 9-504(1)(c)                    Rev. (S)(S) 9-608(a)(1)(C)
                                                                  and 9-615(a)(3)
</TABLE>

          21.4.  Savings Clause. Nothing contained in this (S)21 shall be
                 --------------
     construed to narrow the scope of the Collateral Agent's security interest
     in any of the Collateral or the perfection or priority thereof or to impair
     or otherwise limit any of the rights, powers, privileges or remedies of the
     Collateral Agent, any Noteholder or any Bank hereunder except as (and then
     only to the extent) mandated by Revised Article 9 to the extent then
     applicable.

     22. Miscellaneous. The headings of each section of this Agreement are for
         -------------
convenience only and shall not define or limit the provisions thereof. This
Agreement and all rights and obligations hereunder shall be binding upon each
Company and its respective successors and assigns, and shall inure to the
benefit of the Collateral Agent, the Noteholders, the Banks and their respective
successors and assigns. If any term of this Agreement shall be held to be
invalid, illegal or unenforceable, the validity of all other terms hereof shall
in no way be affected thereby, and this Agreement shall be construed and be
enforceable as if such invalid, illegal or unenforceable term had not been
included herein. Each Company acknowledges receipt of a copy of this Agreement.

                  [Remainder of page intentionally left blank.
                         Next page is signature page.]

                                       9
<PAGE>

     IN WITNESS WHEREOF, intending to be legally bound, the Companies have
caused this Agreement to be duly executed as of the date first above written.

                         ARTHUR D. LITTLE, INC.

                         By: /s/ John F. Burns
                            ---------------------------------
                            John F. Burns
                            Senior Vice President and CFO

                         ARTHUR D. LITTLE INTERNATIONAL, INC.

                         By: /s/ John J. Burns
                            ---------------------------------
                            John F. Burns
                            Vice President

                         ACORN PROPERTIES II, INC.
                         ACORN PROPERTIES III, INC.
                         ACORN PROPERTIES IV, INC.
                         ACORN PROPERTIES VI, INC.
                         ARTHUR D. LITTLE REAL ESTATE
                             CORPORATION
                         G&W SOFTWARE, INC.

                         By: /s/ John F. Burns
                            ---------------------------------
                            John F. Burns
                            President and Treasurer

                         ACORN PROFESSIONAL DEVELOPMENT, INC.
                         ADL NUTRACEUTICALS, INC.
                         ARTHUR D. LITTLE ASIA PACIFIC, INC.
                         ARTHUR D. LITTLE ENTERPRISES, INC.
                         ARTHUR D. LITTLE INDIA, INC.
                         ARTHUR D. LITTLE KOREA, INC.
                           ARTHUR D. LITTLE MANAGEMENT EDUCATION INSTITUTE, INC.
                         ARTHUR D. LITTLE PROGRAM RESOURCES, INC.
                         ENTERPRISE MEDICAL I TECHNOLOGIES, INC.
                         ENTERPRISE COMPUTER, INC.
                         R. DIXON SPEAS ASSOCIATES, INC.

                         By: /s/ John F. Burns
                            ---------------------------------
                            John F. Burns
                            Treasurer

                                       10
<PAGE>

                         INNOVATION ASSOCIATES, INC.
                         PYXSYS CORPORATION

                         By: /s/ John F. Burns
                            ---------------------------------
                            John F. Burns
                            Treasurer

                         ARTHUR D. LITTLE VALUATION, INC.
                         SRT, INC.

                         By: /s/ John F. Burns
                            ---------------------------------
                            John F. Burns
                            Treasurer

                         ADL EUROPE, INC.
                         ADL OVERSEAS, INC.
                         ARTHUR D. LITTLE CIS, INC.
                         ARTHUR D. LITTLE SOUTHEAST ASIA, INC.

                         By: /s/ Frederick T. McElligott
                            ---------------------------------
                            Frederick T. McElligott
                            Treasurer

                         ARTHUR D. LITTLE SECURITIES INVESTMENT, INC.

                         By: /s/ Frederick T. McElligott
                            ---------------------------------
                            Frederick T. McElligott
                            President and Treasurer

Accepted:

CITICORP USA, INC.,
as Collateral Agent

By: /s/ Authorized Officer
    ---------------------------------
    Name:
    Title:

                                       11

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