UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  -------------

                                  SCHEDULE 13D
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                    Under the Securities Exchange Act of 1934
                                (Amendment No.3)*



                             Fair Isaac Corporation
- --------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
- --------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    303250104
- --------------------------------------------------------------------------------
                                 (CUSIP Number)

                         Sandell Asset Management Corp.
                               40 West 57th Street
                                   26th Floor
                               New York, NY 10019
                   Attention: Richard Gashler, General Counsel
                                  212-603-5700

                                 With a Copy to:
                              Marc Weingarten, Esq.
                            Schulte Roth & Zabel LLP
                                919 Third Avenue
                               New York, NY 10019
                                  212-756-2000
- --------------------------------------------------------------------------------
(Name, Address and Telephone Number of Person Authorized to Receive Notices and
                                 Communications)

                                December 4, 2008
                               ------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
[ ].

Note: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.

                          (Continued on following pages)
                               (Page 1 of 9 Pages)

- --------------------
* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page. The information required on the
remainder of this cover page shall not be deemed to be "filed" for the purpose
of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise
subject to the liabilities of that section of the Act but shall be subject to
all other provisions of the Act (however, see the Notes).






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 2 of 9 Pages
- ----------------------------                        ----------------------------

- ------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Castlerigg Master Investments Ltd.
- ------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |_|
- ------------- -----------------------------------------------------------------
     3        SEC USE ONLY
- ------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              WC
- ------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
- ------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              British Virgin Islands
- ------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  2,874,000
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER
                          2,874,000
   WITH
- ------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              2,874,000
- ------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
- ------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              5.9%
- ------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON

              CO
- ------------- -----------------------------------------------------------------






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 3 of 9 Pages
- ----------------------------                        ----------------------------

- ------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Sandell Asset Management Corp.
- ------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |_|
- ------------- -----------------------------------------------------------------
     3        SEC USE ONLY
- ------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
- ------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
- ------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              Cayman Islands
- ------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  2,874,000
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER
                          2,874,000
   WITH
- ------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              2,874,000
- ------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
- ------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              5.9%
- ------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON

              CO
- ------------- -----------------------------------------------------------------






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 4 of 9 Pages
- ----------------------------                        ----------------------------

- ------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Castlerigg International Limited
- ------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |_|
- ------------- -----------------------------------------------------------------
     3        SEC USE ONLY
- ------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
- ------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
- ------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              British Virgin Islands
- ------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  2,874,000
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER
                          2,874,000
   WITH
- ------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              2,874,000
- ------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
- ------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              5.9%
- ------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON

              CO
- ------------- -----------------------------------------------------------------






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 5 of 9 Pages
- ----------------------------                        ----------------------------

- ------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Castlerigg International Holdings Limited
- ------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |_|
- ------------- -----------------------------------------------------------------
     3        SEC USE ONLY
- ------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
- ------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
- ------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              British Virgin Islands
- ------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  2,874,000
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER
                          2,874,000
   WITH
- ------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              2,874,000
- ------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
- ------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              5.9%
- ------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON

              CO
- ------------- -----------------------------------------------------------------






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 6 of 9 Pages
- ----------------------------                        ----------------------------

- ------------- -----------------------------------------------------------------
     1        NAME OF REPORTING PERSON

              Thomas E. Sandell
- ------------- -----------------------------------------------------------------
     2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_|  (b) |_|
- ------------- -----------------------------------------------------------------
     3        SEC USE ONLY
- ------------- -----------------------------------------------------------------
     4        SOURCE OF FUNDS

              AF
- ------------- -----------------------------------------------------------------
     5        CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
              TO ITEMS 2(d) or 2(e)     |_|
- ------------- -----------------------------------------------------------------
     6        CITIZENSHIP OR PLACE OF ORGANIZATION

              Sweden
- ------------- -----------------------------------------------------------------
 NUMBER OF    7           SOLE VOTING POWER

   SHARES                 0
              ----------- -----------------------------------------------------
BENEFICIALLY  8           SHARED VOTING POWER

   OWNED                  2,874,000
              ----------- -----------------------------------------------------
  BY EACH     9           SOLE DISPOSITIVE POWER

 REPORTING                0
              ----------- -----------------------------------------------------
  PERSON      10          SHARED DISPOSITIVE POWER
                          2,874,000
   WITH
- ------------- ----------- -----------------------------------------------------
     11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

              2,874,000
- ------------- -----------------------------------------------------------------
     12       CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
              SHARES |_|
- ------------- -----------------------------------------------------------------
     13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

              5.9%
- ------------- -----------------------------------------------------------------
     14       TYPE OF REPORTING PERSON

              IN
- ------------- -----------------------------------------------------------------






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 7 of 9 Pages
- ----------------------------                        ----------------------------

     The Schedule 13D filed on June 29, 2007, as amended by Amendment No. 1
filed on October 12, 2007 and Amendment No. 2 filed on December 7, 2007 (the
"Schedule 13D") by the Reporting Persons (as defined below), relating to the
common stock, par value $0.01 per share (the "Common Stock"), of Fair Isaac
Corporation, a Delaware corporation (the "Issuer"), is hereby amended as set
forth below by this Amendment No. 3 to the Schedule 13D. Except as set forth
herein, the Schedule 13D is unmodified.

ITEM 2.       IDENTITY AND BACKGROUND

            Paragraph (a) of Item 2 is hereby amended by deleting Castlerigg
Global Select Fund, Limited, CGS, Ltd., and Castlerigg GS Holdings, Ltd. These
entities are no longer reporting persons for purposes of this Schedule 13D as a
result of the merger of CGS, Ltd. and Castlerigg Master Investments Ltd.


ITEM 4.       PURPOSE OF TRANSACTION

            Item 4 of the Schedule 13D is hereby amended and supplemented by the
addition of the following paragraph prior to the final paragraph:

            On December 4, 2008, the Reporting Persons and the Issuer entered
into an amendment to the December 7 Agreement (the "Amended and Restated
December 7 Agreement") pursuant to which, subject to certain conditions: (i) the
Issuer will nominate Nick Graziano, Allan Loren, John S. McFarlane and an
individual selected by the Issuer's board of directors who is reasonably
acceptable to the Reporting Persons for election to the Issuer's board of
directors at the Issuer's 2009 Annual Meeting of Shareholders; (ii) the
Reporting Persons will vote the Common Stock owned by the Reporting Persons in
favor of the above-named nominees and the other persons recommended by the
Issuer's board of directors; (iii) the Reporting Persons (including, as used in
this paragraph, their controlled affiliates) will limit their future acquisition
of Common Stock; (iv) the Reporting Persons will not participate in any proxy
contest in opposition to proposals or matters proposed, recommended or otherwise
supported by the Issuer's board of directors, with limited exceptions relating
to certain publicly-announced transactions involving the Issuer ("Material
Transactions"); (v) the Reporting Persons will not seek to effect a merger or
similar transaction involving the Issuer, with limited exception involving
Material Transactions; (vi) the Reporting Persons will not form a "group" with
unrelated parties; (vii) the Reporting Persons will not publicly disparage any
member of the Issuer's board or management; and (viii) the Reporting Persons
will not publicly seek or request permission to do any of the foregoing, seek to
amend or waive any of the foregoing, or seek permission to make any public
announcement with respect to the foregoing. The restrictions referred to in
clauses (iii) through (viii) will be in effect until the expiration of the
"standstill" period, defined as the period beginning with the execution of the
Amended and Restated December 7 Agreement until the earlier of (a) a date that
is eighty (80) days prior to the date of the Issuer's 2010 Annual Meeting of
Stockholders (absent certain actions being taken by the Issuer's board in the
interim, as described therein) and (b) a material breach by the Issuer of its
obligations under the Amended and Restated December 7 Agreement. Additionally,
under the Amended and Restated December 7 Agreement, the Reporting Persons have
agreed during the "standstill" period to certain restrictions (with certain
exceptions) on their ability to transfer their Common Stock. The foregoing
description of the Amended and Restated December 7 Agreement is a summary only
and is qualified in its entirety by reference to the Amended and Restated
December 7 Agreement, which is attached hereto as Exhibit E.






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 8 of 9 Pages
- ----------------------------                        ----------------------------

ITEM 5.       INTEREST IN SECURITIES OF THE ISSUER

Paragraphs (a) and (c) of Item 5 of the Schedule 13D are hereby amended and
restated as follows:

(a) Each of Castlerigg Master Investments, SAMC, Castlerigg International,
Castlerigg Holdings and Sandell may be deemed to beneficially own the 2,874,000
shares of Common Stock held by Castlerigg Master Investments, representing
approximately 5.9% of the outstanding shares of Common Stock. The Reporting
Persons may be deemed to be a "group," which "group" may be deemed to
beneficially own an aggregate of 2,874,000 shares of Common Stock, representing
approximately 5.9% of the outstanding shares of Common Stock. The percentages
used herein are based upon the 48,477,989 shares of Common Stock reported to be
outstanding as of October 31, 2008 by the Issuer in its annual report on Form
10-K for the period ended September 30, 2008, filed with the Securities and
Exchange Commission on November 26, 2008.

(c) No transactions in the shares of Common Stock were effected by the Reporting
Persons during the past sixty days.


ITEM 6.       CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH
              RESPECT TO SECURITIES OF THE ISSUER

Item 6 of the Schedule 13D is hereby amended by the addition of the following
paragraph:

     As discussed in Item 4 herein, the Reporting Persons and the Issuer entered
into the Amended and Restated December 7 Agreement, involving the nomination of
three individuals selected by the Reporting Persons and one individual selected
by the Issuer and reasonably acceptable to the Reporting Persons to the Issuer's
board of directors and providing for certain standstill undertakings by the
Reporting Persons.

ITEM 7.       MATERIAL TO BE FILED AS EXHIBITS

     The following documents are filed as appendices and exhibits:

Appendix III:   Information Regarding the Instruction C Persons

Exhibit A:    Letter to Issuer's Chief Executive Officer dated June 29, 2007
(previously filed)

Exhibit B:    Press release issued by Sandell Asset Management Corp. on
June 29, 2007 (previously filed)

Exhibit C:    Agreement by and among the Reporting Persons and the Issuer, dated
as of December 7, 2007 (previously filed)

Exhibit D:    Press Release dated December 10, 2007 (previously filed).

Exhibit E:    Amended and Restated Agreement by and among the Reporting Persons
and the Issuer, dated as of December 4, 2008.






- ----------------------------                        ----------------------------
CUSIP No.  303250104            SCHEDULE 13D        Page 9 of 9 Pages
- ----------------------------                        ----------------------------

                                    Signature

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

     Dated: December 8, 2008

            CASTLERIGG MASTER INVESTMENTS LTD.
            By:  Sandell Asset Management Corp.,
                 as investment manager

            By: /s/ Thomas E. Sandell
                ---------------------
                Thomas E. Sandell, Chief Executive Officer


            SANDELL ASSET MANAGEMENT CORP.

            By: /s/ Thomas E. Sandell
                ---------------------
                Thomas E. Sandell, Chief Executive Officer


            CASTLERIGG INTERNATIONAL LIMITED
            By:  Sandell Asset Management Corp.,
                 as investment manager

            By: /s/ Thomas E. Sandell
                ---------------------
                Thomas E. Sandell, Chief Executive Officer


            CASTLERIGG INTERNATIONAL HOLDINGS LIMITED
            By:  Sandell Asset Management Corp.,
                 as investment manager

            By: /s/ Thomas E. Sandell
                ---------------------
                Thomas E. Sandell, Chief Executive Officer


            /s/ Thomas E. Sandell
            ---------------------
            Thomas E. Sandell




                                  Appendix III
                 Information Regarding the Instruction C Persons

Castlerigg Master Investments, SAMC, Castlerigg International and Castlerigg
Holdings have no executive officers or directors other than as follows:

Sandell serves as an executive officer of SAMC.

Sandell Director Services LLC serves as a director of SAMC, Castlerigg Master
Investments, Castlerigg International and Castlerigg Holdings.

Daniel Mignon serves as a director of Castlerigg Master Investments, Castlerigg
International and Castlerigg Holdings.

Hilmi Unver serves as a director of Castlerigg Master Investments, Castlerigg
International and Castlerigg Holdings.

Timothy O'Brien and Richard Gashler serve as executive officers of SAMC.

To the best of the Reporting Persons' knowledge, except as set forth in this
statement on Schedule 13D, none of the Instruction C Persons during the last
five years has been convicted in a criminal proceeding (excluding traffic
violations or other similar misdemeanors) or been a party to a civil proceeding
of a judicial or administrative body of competent jurisdiction and as a result
of such proceeding was or is subject to a judgment, decree or final order
enjoining future violations of, or prohibiting or mandating activities subject
to, federal or state securities laws or finding any violation with respect to
such laws. To the best of the Reporting Persons' knowledge, except as set forth
in this statement on Schedule 13D, none of the Instruction C Persons owns any
shares of Common Stock.

- --------------- ------------------- ---------------------- --------------------
Name            Principal           Address                Citizenship /
                Occupation                                 Place of Organization
- --------------- ------------------- ---------------------- --------------------
Sandell         See Item 2          See Item 2             See Item 2
- --------------- ------------------- ---------------------- --------------------
Sandell         Director Services   c/o Sandell Asset      Delaware
Director                            Management Corp.,
Services LLC                        40 West 57th Street,
                                    26th floor
                                    New York, NY 10019
- --------------- ------------------- ---------------------- --------------------
Mignon          Executive of an     Le Prince de Galles    Belgium
                investment manager  10 Avenue de Grande-
                                    Bretagne
                                    MC-98000 Monte-Carlo
                                    MONACO
- --------------- ------------------- ---------------------- --------------------
Unver           Portfolio Manager   98 Rue de Saint-Jean   Switzerland
                                    case postele 5240
                                    CH-1211 Geneve 11
                                    Switzerland
- --------------- ------------------- ---------------------- --------------------
O'Brien         Chief Financial     40 West 57th Street,   United States
                Officer of          26th Floor
                SAMC                New York, New York
                                    10019
- --------------- ------------------- ---------------------- --------------------
Gashler         General Counsel     40 West 57th Street,   United States
                of SAMC             26th Floor
                                    New York, New York
                                    10019
                         AMENDED AND RESTATED AGREEMENT


          THIS AMENDED AND RESTATED AGREEMENT ("Agreement"), dated the 4th day
of December, 2008 ("Effective Date"), is made by and between Fair Isaac
Corporation, a Delaware corporation (the "Company"), on the one hand, and
Sandell Asset Management Corp., a Cayman Islands exempted company ("SAMC"),
Castlerigg Master Investments Ltd., a British Virgin Islands company
("Castlerigg Master Investments"), Castlerigg International Limited, a British
Virgin Islands company ("Castlerigg International"); Castlerigg International
Holdings Limited, a British Virgin Islands company ("Castlerigg Holdings"
collectively with SAMC, Castlerigg Master Investments, Castlerigg International
and Castlerigg Holdings, the "Sandell Group"), on the other hand.

          WHEREAS, the Sandell Group has filed a Schedule 13D with the
Securities and Exchange Commission (the "SEC") on June 29, 2007, as amended on
October 12, 2007, December 7, 2007 and as may be amended from time to time (the
"Schedule 13D");

          WHEREAS, Directors Guy Henshaw and Tony Christianson have determined
not to stand for re-election to the Company's Board of Directors (the "Board")
at the Company's 2009 Annual Meeting of Stockholders (including any adjournment
or postponement thereof, the "2009 Annual Meeting");

          WHEREAS, the Company and the Sandell Group previously entered into
that certain agreement, dated as of December 7, 2007 (the "Prior Agreement"), to
undertake certain changes to the composition of the Company's Board; and

          WHEREAS, the Company and the Sandell Group desire to amend and restate
the Prior Agreement and have agreed that it is in their mutual interests to
enter into this Agreement as hereinafter described.

          NOW, THEREFORE, in consideration of the premises and the
representations, warranties, and agreements contained herein, and other good and
valuable consideration, the parties hereto mutually agree as follows:

     1.   REPRESENTATIONS AND WARRANTIES OF THE SANDELL GROUP. The Sandell Group
hereby represents and warrants to the Company as follows:

          (a) The Sandell Group has beneficial ownership of 2,874,000 shares of
common stock of the Company and has full power and authority to enter into this
Agreement and to bind the entire number of shares of the common stock of the
Company which it holds, or may hold, including any shares purchased in the
future, to the terms of this Agreement.





          (b) This Agreement constitutes a valid and binding agreement of the
Sandell Group. Except that Thomas E. Sandell may be deemed to beneficially own
shares of the Company and except as set forth in Section 1(a) hereof, no
"affiliate" or "associate" (as such terms are defined in the Securities Exchange
Act of 1934, as amended (the "Exchange Act")) of the Sandell Group beneficially
owns any shares or rights to acquire shares of common stock of the Company.

     2.   REPRESENTATIONS AND WARRANTIES OF THE COMPANY. The Company hereby
represents and warrants to the Sandell Group, as follows:

          (a) The Company has full power and authority to enter into and perform
its obligations under this Agreement, and the execution and delivery of this
Agreement by the Company has been duly authorized by the Board and requires no
further Board or stockholder action, other than amendment of the bylaws of the
Company to increase the size of the Board by two members.

          (b) This Agreement constitutes a valid and binding obligation of the
Company and the performance of its terms does not constitute a violation of its
certificate of incorporation or bylaws.

     3.   DIRECTORSHIPS. The Company agrees that:

          (a) Nick Graziano, Allan Loren, John S. McFarlane and an individual
selected by the Board who is reasonably acceptable to the Sandell Group
(collectively, the "Nominees") will each be nominated by the Board as a director
at the Company's 2009 Annual Meeting of Stockholders (including any adjournment
or postponement thereof, the "2009 Annual Meeting");

          (b) the Company's Board will recommend a vote "for" the Nominees at
the 2009 Annual Meeting, and shall solicit its stockholders to vote for such
Nominees;

          (c) proxies solicited by the Company's Board will be voted "for" the
Nominees at the 2009 Annual Meeting; and

          (d) from the date hereof through the term of his term of office as a
director, each of Mr. Graziano, Mr. Loren and Mr. McFarlane may each be replaced
by another designee of the Sandell Group who is reasonably acceptable to the
Company's Board in the event that Mr. Graziano, Mr. Loren or Mr. McFarlane dies,
is unable to perform his duties as a director, or, in the case of Mr. Graziano,
is no longer associated with the Sandell Group.


                                       2




     4.   VOTING AT MEETINGS OF STOCKHOLDERS.

          (a) At the 2009 Annual Meeting, the Sandell Group shall cause all of
the shares of the Company common stock beneficially owned by it to be present
for quorum purposes and to be voted:

              (i) For each of (A) the Nominees and (B) the other candidates
recommended by the Board in the Schedule 14A filed by the Company with the SEC
for election to the Board (the "Company Nominees"); PROVIDED THAT the Company
Nominees are each either current members of the Board or otherwise reasonably
acceptable to the Sandell Group; and

              (ii) for the ratification of the selection of the Company's
independent auditors.

     5.   THE SANDELL GROUP'S PROHIBITED CONDUCT. During the period commencing
with the execution of this Agreement and ending on the earlier to occur of (a)
the date that is eighty (80) days prior to the date of the Company's 2010 Annual
Meeting of Stockholders (PROVIDED, HOWEVER, that if the Board takes any action
to amend the Company's restated bylaws in such a manner as to increase the time
period prior to the 2010 Annual Meeting of Stockholders by which a holder of the
Company's common stock must provide timely notice to the Company of (i) its
nomination of a person or persons to the Board at a meeting of the Company's
stockholders, (ii) or of its proposal to bring business before a meeting of the
Company's stockholders (clause (i) and (ii) together, the "Stockholder
Matters"), then the Standstill Period (as defined herein) shall expire ten (10)
days prior to the date on which a stockholder must give notice to the Company
with respect to any Stockholder Matters), and (b) a material breach by the
Company of its obligations under this Agreement (the "Standstill Period"),
neither the Sandell Group nor any of its controlled affiliates shall, without
the prior written consent of the Company:

          (a) acquire or agree to acquire, or publicly offer or propose to
acquire, directly or indirectly, by purchase or otherwise, any voting securities
or direct or indirect rights or options to acquire any voting securities of the
Company or any subsidiary thereof, or any assets of the Company or any
subsidiary or division thereof; PROVIDED, HOWEVER, that nothing herein shall
limit the ability of the Sandell Group to (i) transfer any voting securities or
direct or indirect rights or options to acquire any voting securities of the
Company to any of its controlled affiliates, so long as such any such controlled
affiliates agree to be bound by the terms of this Agreement and execute a
joinder agreement to this Agreement, in the form attached hereto as Exhibit A (a
"Joinder Agreement"), (ii) enter into any swap or other arrangement whereby it
acquires the economic consequences of ownership of the common stock without also
acquiring the voting or other rights, privileges or powers associated with the
ownership of the underlying common stock, or (iii) subject to applicable law,
including federal securities laws prohibiting insider trading, acquire up to ten
percent (10%) of the outstanding shares of Company common stock;


                                       3





          (b) other than as provided in this Agreement, seek or propose to
influence or control the management or the policies of the Company (provided
that the Nominees' actions (or those of their replacements as contemplated by
Section 3) as members of the Board shall not be deemed to violate the foregoing)
or to obtain representation on the Board (other than the nomination of the
Nominees), directly or indirectly engage in any activities in opposition to the
recommendation of the Board (including the recommendation of the Nominees and
the Company Nominees as directors to be elected at the 2009 Annual Meeting),
submit any proposal (whether pursuant to Rule 14a-8 or otherwise) or nomination
of a director or directors for stockholder action, or solicit, or encourage or
in any way participate in the solicitation of, any proxies or consents with
respect to any voting securities of the Company, PROVIDED, HOWEVER, that the
foregoing shall not prohibit the Sandell Group from (i) making public statements
(including statements contemplated by Rule 14a-1(1)(2)(iv) under the Exchange
Act), or (ii) engaging in discussions with other stockholders or (iii)
soliciting, or encouraging or participating in the solicitation of, proxies or
consents with respect to voting securities of the Company (so long as such
discussions are in compliance with subsection (d) hereof (clauses (i), (ii) and
(iii), together, "Permitted Actions") with respect to any transaction that has
been publicly announced by the Company involving (1) the recapitalization of the
Company, (2) an acquisition, disposition or sale of assets or a business by the
Company where (A) the consideration to be received or paid in such transaction
exceeds $400 million in the aggregate or (B) requires approval by the holders of
common stock of the Company, or (3) a change of control of the Company (each, a
"Material Transaction"), PROVIDED, FURTHER, that in the event that one of the
Nominees votes against an acquisition, disposition or sale of assets or a
business by the Company, which is neither a Material Transaction nor an
acquisition, disposition or sale of assets or a business by the Company where
the consideration to be received or paid in such transaction is less than $125
million in the aggregate, at the Board meeting approving such transaction, the
Company will make a public statement that such Nominee so voted;

          (c) make any public announcement with respect to, or publicly offer to
effect, seek or propose (with or without conditions) a merger, consolidation,
business combination or other extraordinary transaction with or involving the
Company or any of its subsidiaries or any of its or their securities or assets,
PROVIDED, HOWEVER, that nothing in this subsection (c) shall restrict the
Sandell Group from taking Permitted Actions with respect to a Material
Transaction;

          (d) (i) form, join or in any way participate in a "group" as defined
in Section 13(d)(3) of the Exchange Act, and the rules and regulations
promulgated thereunder, other than a "group" that includes all or some lesser
number of persons identified as members of the Sandell Group, or (ii) enter into
any negotiations, arrangements or understandings with any third parties, other
than members of the Sandell Group solely with respect to the existing members of
the Sandell Group, in connection with becoming a "group" as defined in Section
13(d)(3) of the Exchange Act;

          (e) publicly disparage any member of the Board or management of the
Company; or


                                       4





          (f) publicly seek or request permission to do any of the foregoing,
request to amend or waive any provision of this Section 5 (including, without
limitation, any of clauses (a)-(e) hereof), or make or seek permission to make
any public announcement with respect to any of the foregoing.

     6.   TRANSFER RESTRICTIONS. The Sandell Group agrees that, during the
Standstill Period, it shall not offer, pledge, sell, contract to sell, sell any
option or contract to purchase, purchase any option or contract to sell, grant
any option, right or warrant to purchase, lend (other than in a customary
commingled brokerage account in the ordinary course of business), or otherwise
transfer or dispose of, directly or indirectly, any shares of common stock or
any securities convertible into or exercisable or exchangeable, directly or
indirectly, for common stock, whether any such transaction described above is to
be settled by delivery of common stock or such other securities, in cash or
otherwise (any such action a "Transfer"), in each case without the prior written
consent of the Company; PROVIDED THAT the foregoing shall not restrict the
Sandell Group from (i) a Transfer of any shares to a controlled affiliate which
agrees to be bound by the terms of this Agreement and executes a Joinder
Agreement, (ii) subject to compliance with law, the Transfer of shares in either
(1) brokers' transactions (within the meaning of Rule 144(g) of the Securities
Act of 1933 (the "Securities Act")), but not in transactions directly with a
market maker (as defined in Section 3(a)(38) of the Exchange Act), or (2)
private Transfers (including transactions with, or indirectly through, a market
maker), in a single Transfer or series of related Transfers, so long as the
Sandell Group, at the time of such Transfer, does not have actual knowledge,
after reasonable inquiry, that such Transfer or series of Transfers would result
in the ultimate purchaser of such shares of common stock from the Sandell Group
beneficially owning, together with its affiliates, following such Transfer or
Transfers, in excess of five percent (5%) of the Company's common stock in the
aggregate, or (iii) Transfers made pursuant to (x) tender offers in respect of
the Company's common stock made by the Company or any third party, or (y)
repurchase offers in respect of the Company's common stock made directly with
the Company.

     7.   RESIGNATION. Each of Mr. Graziano, Mr. Loren and Mr. McFarlane (and
any replacement director appointed to the Board pursuant to Section 3(d)) shall
immediately tender his resignation from the Board, if requested by the Board as
a result of a majority vote of the directors, other than the Nominees, in favor
of such resignations from the Board, in the event that the Sandell Group's
beneficial ownership of the Company's common stock becomes less than three
percent (3%) of the outstanding shares of common stock of the Company solely as
a result of a Transfer or series of Transfers by the Sandell Group.

     8.   NONDISPARAGEMENT. During the Standstill Period, the Company shall not
publicly disparage the Sandell Group or any member of the management of the
Sandell Group.

     9.   PUBLIC ANNOUNCEMENT. The Company shall disclose the existence of this
Agreement after its execution pursuant to a Company press release reasonably
acceptable to the Sandell Group; HOWEVER, neither party shall disclose the
existence of this Agreement until the press release is issued except as
otherwise required by applicable law, rule or regulation and


                                       5




provided that the non-disclosing party is provided a reasonable opportunity to
review and comment upon any such disclosure and the disclosing party considers
in good faith any such comments provided by the non-disclosing party.

     10.  REMEDIES. The Company and the Sandell Group acknowledge and agree that
a breach or threatened breach by either party may give rise to irreparable
injury inadequately compensable in damages, and accordingly each party shall be
entitled to injunctive relief to prevent a breach of the provisions hereof and
to enforce specifically the terms and provisions hereof in any state or federal
court having jurisdiction, in addition to any other remedy to which such
aggrieved party may be entitled to at law or in equity. In the event either
party institutes any legal action to enforce such party's rights under, or
recover damages for breach of, this Agreement, the prevailing party or parties
in such action shall be entitled to recover from the other party or parties all
costs and expenses, including but not limited to reasonable attorneys' fees,
court costs, witness fees, disbursements and any other expenses of litigation or
negotiation incurred by such prevailing party or parties.

     11.  NOTICES. All notice requirements and other communications shall be
deemed given when delivered or on the following business day after being sent by
overnight courier with a nationally recognized courier service such as Federal
Express, addressed to the Company, SAMC, Castlerigg Master Investments,
Castlerigg International, Castlerigg Holdings and Mr. Sandell as follows:


                  THE COMPANY:

                  Fair Isaac Corporation
                  901 Marquette Avenue, Suite 3200
                  Minneapolis, MN 55402-3232
                  Facsimile:  (612) 758-6002
                  Attention: General Counsel

                  With a copy to (which shall not constitute notice):

                  Skadden, Arps, Slate, Meagher & Flom LLP
                  525 University Avenue, Suite 1100
                  Palo Alto, California 94301
                  Facsimile:  (650) 470-4570
                  Attention:  Kenton J. King
                                M. Amr Razzak

                  THE SANDELL GROUP:

                  Sandell Asset Management Corp.
                  40 W 57th Street, 26th Floor
                  New York, NY 10019
                  Facsimile: (212) 603-5725


                                       6





                  Attn: General Counsel

                  with copies to (which shall not constitute notice):

                  Schulte Roth & Zabel LLP
                  919 Third Avenue
                  New York, NY 10022
                  Facsimile: (212) 593-5955
                  Attention:  Marc Weingarten

     12.  ENTIRE AGREEMENt. This Agreement constitutes the entire agreement
between the parties hereto pertaining to the subject matter hereof and
supersedes all prior and contemporaneous agreements understandings, negotiations
and discussions of the parties in connection therewith not referred to herein.

     13.  COUNTERPARTS; FACSIMILE. This Agreement may be executed in any number
of counterparts and by the parties hereto in separate counterparts, and
signature pages may be delivered by facsimile, 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.

     14. HEADINGS. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

     15.  GOVERNING LAW. This Agreement shall be governed by and construed and
enforced in accordance with the laws of the State of Delaware, without regard to
choice of law principles that would compel the application of the laws of any
other jurisdiction.

     16.  SEVERABILITY. In the event one or more of the provisions of this
Agreement should, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect any other provisions of this Agreement, and this Agreement
shall be construed as if such invalid, illegal or unenforceable provision had
never been contained herein.

     17.  SUCCESSORS AND ASSIGNS. This Agreement shall not be assignable by any
of the parties to this Agreement. This Agreement, however, shall be binding on
successors of the parties hereto.

     18.  SURVIVAL OF REPRESENTATIONS, WARRANTIES AND AGREEMENTS. All
representations, warranties, covenants and agreements made herein shall survive
the execution and delivery of this Agreement.


                                       7





     19.  AMENDMENTS. This Agreement may not be modified, amended, altered or
supplemented except upon the execution and delivery of a written agreement
executed by all of the parties hereto.

     20.  FURTHER ACTION. Each party agrees to execute any and all documents,
and to do and perform any and all acts and things necessary or proper to
effectuate or further evidence the terms and provisions of this Agreement.

     21.  CONSENT TO JURISDICTION. Each of the parties hereby irrevocably
submits to the exclusive jurisdiction of any state court sitting in the State of
Delaware in any action or proceeding arising out of or relating to this
Agreement and each of the parties hereby irrevocably agrees that all claims in
respect of such action or proceeding may be heard and determined in any such
court.

     22.  EXPENSES. Each party agrees to bear its own expenses in connection
with the transactions contemplated hereby.



                            [SIGNATURE PAGE FOLLOWS]
























                                       8








              The Company and the Sandell Group each indicate its agreement
with the foregoing by signing and returning one copy of this agreement,
whereupon this letter agreement will constitute their agreement with respect to
the subject matter hereof.


Accepted to and agreed,
as of the date first written above:


FAIR ISAAC CORPORATION

By:     /s/ Mark N. Greene
        --------------------------
Name:   Mark N. Greene
Title:  CEO


SANDELL ASSET MANAGEMENT CORP.

By:     /s/ Thomas E. Sandell
        --------------------------
Name:   Thomas E. Sandell
Title:  Chief Executive Officer


CASTLERIGG MASTER INVESTMENTS LTD.
BY: SANDELL ASSET MANAGEMENT CORP.

By:     /s/ Thomas E. Sandell
        --------------------------
Name:   Thomas E. Sandell
Title:  Chief Executive Officer


CASTLERIGG INTERNATIONAL LIMITED
BY: SANDELL ASSET MANAGEMENT CORP.

By:     /s/ Thomas E. Sandell
        --------------------------
Name:   Thomas E. Sandell
Title:  Chief Executive Officer


CASTLERIGG INTERNATIONAL HOLDINGS LIMITED
BY: SANDELL ASSET MANAGEMENT CORP.

By:     /s/ Thomas E. Sandell
        --------------------------
Name:   Thomas E. Sandell
Title:  Chief Executive Officer







                                    EXHIBIT A


                            FORM OF JOINDER AGREEMENT


The undersigned hereby agrees, effective as of the date hereof, to become a
party to that certain Amended and Restated Agreement, dated as of December [o],
2008, by and among Fair Isaac Corporation, a Delaware corporation (the
"Company"), Sandell Asset Management Corp., a Cayman Islands exempted company
("SAMC"), Castlerigg Master Investments Ltd., a British Virgin Islands company
("Castlerigg Master Investments"), Castlerigg International Limited, a British
Virgin Islands company ("Castlerigg International"); Castlerigg International
Holdings Limited, a British Virgin Islands company ("Castlerigg Holdings" and
collectively with SAMC, Castlerigg Master Investments, Castlerigg International
and Castlerigg Holdings, the "Sandell Group") (the "Agreement"). By executing
this joinder agreement, the undersigned hereby agrees to be, and shall be,
deemed a member of the "Sandell Group" for all purposes of the Agreement,
entitled to the rights and subject to the obligations thereunder with respect to
the voting securities of the Company acquired from the Sandell Group.


The address and facsimile number to which notices may be sent to the undersigned
is as follows:


                  Facsimile No.:




By:
       --------------------------------

Name:
       --------------------------------

Title:
       --------------------------------

Date:
       --------------------------------




                                       A-1