<PAGE>
                                                                     EXHIBIT 4.2

THIS NOTE AND ANY SECURITIES ISSUABLE UPON THE CONVERSION OF THIS NOTE HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE
TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS THEY HAVE BEEN REGISTERED UNDER SUCH
ACT OR PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT.



                                  ENGAGE, INC.

                      7.5% Secured Convertible Demand Note


                                                                 October 4, 2001

         FOR VALUE RECEIVED, the undersigned, Engage, Inc., a Delaware
corporation (the "Borrower"), hereby promises to pay to CMGI, Inc., a Delaware
corporation (the "Lender"), or order, ON DEMAND (in full or in part, at Lender's
choice in its sole discretion) in immediately available funds in lawful money of
the United States of America, at the offices of CMGI, Inc., the principal amount
of outstanding intercompany debt incurred by the Borrower during each calendar
month from October 2001 to July 2002, inclusive, together with accrued but
unpaid interest thereon. The intercompany debt incurred by Borrower during each
calendar month and that is subject to this Note shall be acknowledged by the
Borrower and Lender on the attached SCHEDULE A (the principal amount of
outstanding intercompany debt incurred by the Borrower in each calendar month
and due hereunder shall be referred to as the "Monthly Principal Amount" and the
entire principal amount due hereunder shall be referred to as the "Principal
Amount"). Interest on the Principal Amount shall be at a rate of 7.5% per annum
("Interest"), calculated on the basis of a 360-day year consisting of twelve 30
day months and compounded and payable quarterly in arrears on October 31,
January 31, April 30 and July 31 and of each year until this Note is paid in
full (each an "Interest Payment Date"). The Interest on each Monthly Principal
Amount shall accrue on the first day of the calendar month following the
calendar month in which such debt was incurred. If all or a portion of the
Principal Amount or Interest shall not be paid when due, the Borrower hereby
promises to pay, on demand, interest on such overdue amount and every other
amount due under this Note thereafter, from and including the demand date to,
but excluding, the date such amount is paid in full at 9.5% per annum (and until
the date such overdue amount is paid in full, "Interest" on such overdue amount
shall mean interest at such rate). In no event shall holder demand payment of
any principal or interest until August 1, 2002. Interest payment for the
quarters ending October 31, 2001, January 31, 2002,

                                       1
<PAGE>

April 30, 2002 and July 31, 2002 shall be deferred until, and shall become
payable on, August 1, 2002.

         1.       Payment.

                  Payment of the Principal Amount on the date Lender demands
payment and Interest on each Interest Payment Date shall be made by certified or
bank cashier's check payable to the Lender at the Lender's principal address set
forth in Section 6 hereof (or at such other place as the Lender hereof shall
notify the Borrower in writing) or, if the Lender so specifies, by written
notice to the Borrower given not less than five business days prior to the
Interest funds, to the account so specified, in lawful money of the United
States of America, PROVIDED THAT, at the election of the Lender, by written
notice to the Borrower given not less than five business days prior to the
Interest Payment Date, the amount of Interest due on any Interest Payment Date
may be paid in shares of common stock, par value $0.01 per share ("Common
Stock"), of the Borrower, in the manner set forth in Section 2(a) hereof. The
Borrower may, upon ten days written notice to Lender giving Lender the
opportunity to convert this Note as provided herein, prepay this Note in cash at
any time, without premium or penalty, in whole or in part, with accrued interest
to the date of such payment on the amount prepaid. Payment of this Note is
secured by a security interest in substantially all property of the Borrower
(the "Collateral") pursuant to a security agreement of even date herewith
between the Borrower and the Lender (the "Security Agreement"). The rights of
holder under this Note are in addition to any other rights and remedies
(including other rights of setoff) which holder may have. The holder shall be
permitted to exercise its rights as a secured party under the Security Agreement
to the extent permitted by applicable law.

         2.       Conversion.

                  (a) CONVERSION RIGHTS. Subject to and in accordance with the
provisions of this Section 2, the Lender may elect, in its sole discretion, and
at any time following the date hereof, to effect the conversion (the
"Conversion") of each Monthly Principal Amount and any/or Interest outstanding
thereon on into the number of shares of Common Stock determined by dividing such
Monthly Principal Amount and/or Interest due thereon by the closing price per
share of the Common Stock on the Nasdaq National Market as reported in The Wall
Street Journal on the last trading day of such calendar month in which the
Monthly Principal Amount was accrued (the "Conversion Price"). The Conversion
Price is subject to adjustment as provided in Section 3 hereof.


                                      2
<PAGE>

                  (b) MANNER OF EFFECTING THE CONVERSION. If the Lender elects
to effect the Conversion pursuant to Section 2(a) hereof, the Lender shall
deliver a duly executed written notice to the Borrower of such election (the
"Conversion Notice"), and in such event the Conversion shall be deemed to have
been effected at the close of business on the date such Conversion Notice is
given. Upon any Conversion of this Note in accordance with the terms hereof, the
rights of the Lender with respect to the Principal Amount and all Interest
pursuant to this Note shall cease and the Lender shall be deemed to have become
the holder of record of the shares of Common Stock into which this Note shall
have been converted, PROVIDED THAT, if the Lender elects to convert only a
portion of the Principal Amount and Interest pursuant to Section 2(a) hereof,
then the Borrower will deliver a new note to the Lender, on the same terms and
conditions as this Note, with respect to the portion of the Principal Amount and
Interest that is not converted (the "New Note"). Concurrently with the delivery
of a Conversion Notice, the Lender shall surrender this Note to the Borrower
free and clear of all liens and encumbrances. Promptly upon its receipt of a
Conversion Notice, the Borrower shall (i) deliver to or upon the written order
of the Lender, a certificate or certificates for the number of shares of Common
Stock issuable upon such Conversion, (ii) make a cash payment in respect of any
fraction of a share as provided in Section 2(c) hereof and (iii) if applicable,
deliver a New Note as set forth in this Section 2(b).

                  (c) FRACTIONAL SHARES. No fractional shares shall be issued
upon any Conversion. Instead of any fractional share which would otherwise be
issuable upon a Conversion, the Borrower shall pay a cash amount equal to such
fractional share multiplied by the Conversion Price.


         3.       Antidilution Provisions.

                  (a) REORGANIZATION, RECLASSIFICATION OR RECAPITALIZATION OF
THE BORROWER. In case of (i) a capital reorganization, reclassification or
recapitalization of the Borrower's capital stock (other than in the cases
referred to in Section 3(c) hereof), (ii) the Borrower's consolidation or merger
with or into another corporation in which the Borrower is not the surviving
entity, or a merger in which the Borrower is the surviving entity but the shares
of the Borrower's capital stock outstanding immediately prior to the merger are
converted, by virtue of the merger, into other property, whether in the form of
securities, cash or otherwise, or (iii) the sale or transfer of all or
substantially all of the Borrower's assets, then, as part of such
reorganization, reclassification, recapitalization, merger, consolidation, sale
or transfer, lawful provision shall be made so that there shall thereafter be
deliverable upon the Conversion of the Principal Amount and Interest or any
portion thereof (in lieu of or in addition to the number of shares of Common
Stock theretofore deliverable, as appropriate) and without payment of any
additional consideration, the number of shares of stock or other securities or
property to which the holder of the

                                       3

<PAGE>

number of shares of Common Stock which would otherwise have been deliverable
upon the Conversion of the Principal Amount and Interest or any portion thereof
at the time of such reorganization, reclassification, recapitalization,
consolidation, merger, sale or transfer would have been entitled to receive in
such reorganization, reclassification, recapitalization, consolidation, merger,
sale or transfer. This Section 3(a) shall apply to successive reorganizations,
reclassifications, recapitalizations, consolidations, mergers, sales and
transfers and to the stock or securities of any other corporation that are at
the time receivable upon the Conversion of the Principal Amount and Interest or
any portion thereof. If the per share consideration payable to the Lender for
shares of Common Stock in connection with any transaction described in this
Section 3(a) is in a form other than cash or marketable securities, then the
value of such consideration shall be determined in good faith by the Borrower's
board of directors.

                  (b) SPLITS AND COMBINATIONS. If the Borrower at any time or
from time to time after the date of this Note subdivides any of its outstanding
shares of Common Stock into a greater number of shares, the Conversion Price in
effect immediately prior to such subdivision shall be proportionately reduced,
and, conversely, if the outstanding shares of Common Stock are combined into a
smaller number of shares, the Conversion Price in effect immediately prior to
such combination shall be proportionately increased.

                  (c) RECLASSIFICATIONS. If the Borrower reclassifies or
otherwise changes any of the securities into which this Note may be convertible
into the same or a different number of securities of any other class or classes,
this Note shall thereafter be convertible into such number and kind of
securities as would have been issuable as the result of such change with respect
to the securities that this Note was convertible into immediately prior to such
reclassification or other change and the Conversion Price therefor shall be
appropriately adjusted.

                  (d) ADJUSTMENT CERTIFICATES. Upon any adjustment of the
Conversion Price or the number of shares of Common Stock issuable upon the
Conversion of this Note, a certificate, signed by (i) the Borrower's President
and Chief Financial Officer or (ii) any independent firm of certified public
accountants of recognized national standing the Borrower selects at its own
expense, setting forth in reasonable detail the events requiring the adjustment
and the method by which such adjustment was calculated, shall be mailed to the
Lender at the address set forth in Section 5 hereof and shall specify the
adjusted Conversion Price and the number of shares of Common Stock issuable upon
the Conversion of the Note after giving effect to the adjustment.

                  (e) ISSUANCE OF RIGHTS OR WARRANTS. In case the Borrower shall
issue to all holders of Common Stock rights or warrants entitling such holders
to subscribe for or purchase Common Stock at a price per share less than the
Current

                                       4
<PAGE>

Market Price, the Conversion Price in effect immediately prior to the
close of business on the record date fixed for determination of stockholders
entitled to receive such rights or warrants shall be reduced by multiplying such
Conversion Price by a fraction, the numerator of which is the sum of the number
of shares of Common Stock outstanding at the close of business on such record
date and the number of shares of Common Stock so offered for subscription or
purchase would purchase at such Current Market Price and the denominator of
which is the sum of the number of shares of outstanding at the close of business
on such record date and the number of additional shares of Common Stock so
offered for subscription or purchase. For purposes of this subparagraph, the
issuance of rights or warrants to purchase the Common Stock into which such
securities are convertible at an aggregate offering price equal to the sum of
the aggregate offering price of such securities and the minimum aggregate amount
(if any) payable upon conversion of such securities into Common Stock. Such
adjustment shall be made successively whenever any such event shall occur.

                  (f) ISSUANCE OF COMMON STOCK. In case the Borrower shall issue
or sell any shares of Common Stock at a price per share less than the Current
Market Price (other than any (i) such transaction as to which an adjustment is
otherwise provided for in this Section 3, (ii) the issuance of any Common Stock
to CMGI, Inc. or any affiliate thereof or (iii) the issuance by the Company to
directors, employees, consultants or advisors of the Borrower of shares of
Common Stock, or grant of options or other rights to purchase or acquire Common
Stock, at a price, or exercise price, as the case may be, no lower the fair
market value of the Common Stock (as reasonably determined by the independent
directors of the Company in good faith as of the time of issuance or grant, as
the case may be)), the Conversion Price in effect immediately prior to the close
of business on the date immediately preceding such issuance or sale shall be
reduced by multiplying such Conversion Price by a fraction, the numerator of
which is the sum of the number of shares of Common Stock outstanding at the
close of business on the date immediately preceding such issuance or sale to and
the number of shares of Common Stock that the aggregate price paid for the total
number of shares of Common Stock so issued or sold on such date would purchase
at such Current Market Price and the denominator of which is the sum of the
number of shares of Common Stock outstanding at the close of business on the
date immediately preceding such issuance or sale and the number of additional
shares of Common Stock so issued or sold. For purposes of this subparagraph, the
issuance of rights, options or warrants to purchase the Common Stock or
securities exchangeable for Common Stock shall be deemed issuance of Common
Stock into which such securities are exercisable at an aggregate price equal to
the sum of the aggregate price paid for such securities and the minimum
aggregate amount (if any) payable upon exercise or conversion of such options,
rights, warrants, or securities for Common Stock, and the date of issuance and
sale for purposes hereof shall be the date upon which such options, rights or
warrants, were issued or amended. Such adjustment shall be made successively
whenever any such

                                       5
<PAGE>

event shall occur; provided that no adjustment shall be made upon exercise
of any option, right or warrant. If any adjustment is made as the result
of the issuance of an option, right, warrant or convertible security and
such option, right, warrant or security expires unexercised or unconverted, the
Conversion Price shall be readjusted to the price that would have been in effect
if no adjustment had been made.


                  (g) NO IMPAIRMENT. The Borrower shall not, by amendment of its
Certificate of Incorporation or through any reorganization, recapitalization,
transfer of assets, consolidation, merger, dissolution, issue or sale of
securities or any other voluntary action, avoid or seek to avoid the observance
or performance of any of the terms to be observed or performed hereunder by the
Borrower, but shall at all times in good faith assist in the carrying out of all
provisions of this Section 3 and in the taking of all such action as may be
necessary or appropriate in order to protect the rights of the Lender against
impairment. No reference in this Note to the Security Agreement or any guaranty
shall impair the obligation of the Borrower, which is absolute and
unconditional, to pay all amounts under this Note strictly in accordance with
the terms of this Note.

                  (h) APPLICATION. Except as otherwise provided herein, all
sections of this Section 3 are intended to operate independently of one another.
If an event occurs that requires the application of more than one section, all
applicable sections shall be given independent effect.

         4.       Default and Remedies.

         This Note shall become immediately due and payable without notice or
demand upon the occurrence at any time of any of the following events of default
(individually, "an Event of Default" and collectively, "Events of Default"):

                           (i) default in the payment or performance of this or
                  any other liability or obligation of the Borrower to the
                  holder, including the payment when due of any principal,
                  premium or interest under this Note;

                           (ii) the occurrence of any event of default under
                  the Security Agreement;

                           (iii) the liquidation, termination of existence,
                  dissolution, insolvency or business failure of the Borrower,
                  or the appointment of a receiver or custodian for the Borrower
                  or any part of its; or

                           (iv) the institution by or against the Borrower or
                  any indorser or guarantor of this Note of any proceedings
                  under the United States Bankruptcy Code or any other federal
                  or state bankruptcy,

                                       6
<PAGE>

                  reorganization, receivership, insolvency or other similar
                  law affecting the rights of creditors generally or the
                  making by the Borrower or any indorser or guarantor of this
                  Note of a composition or an assignment or trust mortgage for
                  the benefit of creditors.

        Upon the occurrence of an Event of Default, the holder shall have then,
        or at any time thereafter, all of the rights and remedies afforded by
        the Uniform Commercial Code as from time to time in effect in The
        Commonwealth of Massachusetts or afforded by other applicable law.


         5.       Notices

                  All notices, instructions and other communications given
hereunder or in connection herewith shall be in writing. Any such notice,
instruction or communication shall be sent either (i) by certified mail, return
receipt requested, postage prepaid, (ii) via a reputable nationwide overnight
courier service or (iii) by facsimile (with "answer-back" confirmation), in each
case to the address set forth below. Any such notice, instruction or
communication shall be deemed to have been delivered upon receipt of
confirmation of delivery after it is sent by certified mail, return receipt
requested, postage prepaid, one business day after it is sent via a reputable
nationwide overnight courier service, or upon receipt of confirmation of
delivery of a facsimile.

If to the Borrower to:           Engage, Inc.
                                 100 Brickstone Square
                                 Andover, MA 01810
                                 Attention: General Counsel

If to the Lender to:             CMGI, Inc.
                                 100 Brickstone Square
                                 Andover, MA 01810
                                 Attention:  William Williams, II, Esq.
                                 Facsimile:  (978) 684-3601


Either party may give any notice, instruction or communication in connection
with this Note using any other means (including personal delivery or ordinary
mail), but no such notice, instruction or communication shall be deemed to have
been delivered unless and until it is received by the party to whom it was sent.
Either party may change the address to which notices, instructions or
communications are to be delivered by giving the other party to this Note notice
thereof in the manner set forth in this Section 5.

                                       7
<PAGE>

         6.       Miscellaneous.

                  This Note shall be construed and enforced in accordance with
the laws of the Commonwealth of Massachusetts, without regard to its conflicts
of laws rules. The Borrower waives presentment, notice, protest and all other
notices in connection with the delivery, acceptance, performance, default and
enforcement of this Note. The Borrower hereby irrevocably and unconditionally
submits, for itself and its property, to the non-exclusive jurisdiction of the
courts of the Commonwealth of Massachusetts and of the United States District
Court for the District of Massachusetts, and any appellate court of such courts,
in any action or proceeding arising out of or relating to this Note, or for
recognition or enforcement of any judgment, and the Borrower hereby irrevocably
and unconditionally agrees that all claims in respect of any such action or
proceeding may be heard and determined in such Massachusetts court (or, to the
extent permitted by law, in such federal court). The Borrower agrees that a
final, unappealable 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 Note shall affect any right
that the Lender may otherwise have to bring any action or proceeding relating to
this Note against the Borrower or its properties in the courts of any
jurisdiction.

THE LENDER AND THE BORROWER AGREE THAT NEITHER OF THEM NOR ANY ASSIGNEE OR
SUCCESSOR SHALL (A) SEEK A JURY TRIAL IN ANY LAWSUIT, PROCEEDING, COUNTERCLAIM
OR ANY OTHER ACTION BASED UPON, OR ARISING OUT OF, THIS NOTE, ANY RELATED
INSTRUMENTS, ANY COLLATERAL OR THE DEALINGS OR THE RELATIONSHIP BETWEEN OR AMONG
ANY OF THEM, OR (B) SEEK TO CONSOLIDATE ANY SUCH ACTION WITH ANY OTHER ACTION IN
WHICH A JURY TRIAL CANNOT BE OR HAS NOT BEEN WAIVED. THE PROVISIONS OF THIS
PARAGRAPH HAVE BEEN FULLY DISCUSSED BY THE LENDER AND THE BORROWER, AND THESE
PROVISIONS SHALL BE SUBJECT TO NO EXCEPTIONS. NEITHER THE LENDER NOR THE
BORROWER HAS AGREED WITH OR REPRESENTED TO THE OTHER THAT THE PROVISIONS OF THIS
PARAGRAPH WILL NOT BE FULLY ENFORCED IN ALL INSTANCES.

                  If any provision of this Note shall be held invalid or
unenforceable by any court of competent jurisdiction, that holding shall not
invalidate or render unenforceable any other provision hereof.

                  This Note and all rights hereunder are freely transferable by
the holder hereof, subject to compliance with applicable state and federal
securities laws.

                                       8
<PAGE>

                  This Note may not be changed, amended or modified except by
agreement in writing signed by the Borrower and the Lender.


            7.    Certain Definitions.

            As used herein, the following terms have the following meanings:

         "CLOSING PRICE" shall mean, on any day, (i) the closing price of the
Common Stock (or any other security for which a closing price must be
determined) on a national securities exchange or as quoted on the Nasdaq
National Market on such day, as reported by the Wall Street Journal or (ii) if
the Common Stock (or any such other security) is quoted on the Nasdaq National
Market but no sale occurs on such day, the average of the closing bid and asked
prices of the Common Stock (or any such other security) on the Nasdaq National
Market on such day, as reported by the Wall Street Journal or (iii) if the
Common Stock (or any such other security) is not so listed or quoted, the
average of the closing bid and asked prices of the Common Stock (or any such
other security) in the U.S. over-the-counter market or (iv) if no such trading
market is readily available, the fair market value of the Common Stock as
reasonably determined by the independent directors of the Company in good faith.

         "CURRENT MARKET PRICE" of the Common Stock means the average of the
daily Closing Prices of the Common Stock for the five consecutive trading days
selected by the board of directors commencing not more than 20 trading days
before, and ending not later than the date immediately preceding the record date
fixed in connection with such event or, if there is no record date, the date of
such event.

            [The remainder of this page is intentionally left blank.]


                                       9

<PAGE>

                  IN WITNESS WHEREOF, the Borrower has caused this Note to be
signed on its behalf, in its corporate name, by its duly authorized officer as
an instrument under seal, as of the day and year first above written.


                                          ENGAGE, INC.



                                          By: /s/ Christopher Cuddy
                                              ----------------------------------
                                              Name:  Christopher Cuddy
                                              Title: Chief Executive Officer


                                       10
<PAGE>
                                   SCHEDULE A

                            Monthly Intercompany Debt
<TABLE>
<CAPTION>
----------------------- ----------------------- -------------------------- ------------------- ---------------------
CALENDAR MONTH          CLOSING PRICE OF        PRINCIPAL AMOUNT OF        SIGNATURE OF        SIGNATURE OF
                        COMMON STOCK ON LAST    INTERCOMPANY DEBT          LENDER              BORROWER
                        TRADING DAY OF SUCH     INCCURED IN SUCH MONTH
                        MONTH
----------------------- ----------------------- -------------------------- ------------------- ---------------------
<S>                     <C>                      <C>                       <C>                 <C>
October 2001
----------------------- ----------------------- -------------------------- ------------------- ---------------------
November 2001
----------------------- ----------------------- -------------------------- ------------------- ---------------------
December 2001
----------------------- ----------------------- -------------------------- ------------------- ---------------------
January 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
February 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
March 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
April 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
May 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
June 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
July 2002
----------------------- ----------------------- -------------------------- ------------------- ---------------------
</TABLE>






                                       11