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