<PAGE>


                                                                   Exhibit 10.24


December 13, 1999


Mr. Raymond V. Thomas


Re:      SEPARATION TERMS

Dear Mr. Thomas:

This letter agreement (this "AGREEMENT") confirms the terms of the termination
of your employment with HNC Software Inc. ("HNC"). This Agreement is also
intended to address the consulting services which you may hereafter provide to
HNC and its subsidiary eHNC, Inc. ("EHNC"), and to permanently resolve any and
all potential disputes which may arise concerning your employment with HNC, or
the termination of your employment with HNC.

1. EMPLOYMENT TERMINATION DATE: You agree that your employment with HNC will be
terminated effective on February 28, 2000 (the "TERMINATION DATE"). You
acknowledge and agree that you will cease to hold the offices of Vice President,
Finance and Administration and Chief Financial Officer effective as of January
15, 2000, but you will nevertheless continue to serve as a full-time employee
through the Termination Date. Between January 15, 2000 and the Termination Date
it is expected that you will primarily work with your successor to the office of
Chief Financial Officer in order to assist in effecting an orderly transition in
duties. You also agree to resign as an officer of eHNC and to resign from the
Board of Directors of eHNC immediately, if at any time after the Termination
Date HNC or eHNC requests you to do so.

2. PAYMENT OF WAGES: On or before the Termination Date, we shall deliver to you
a final paycheck which shall include all accrued wages, salary, bonuses,
reimbursable expenses, accrued but unused vacation pay and any similar payments
due and owing to you from HNC as of the Termination Date. We will deduct all
normal tax withholdings and other required deductions from these payments.

3. STOCK OPTIONS.

         (a) STATUS OF HNC AND EHNC STOCK OPTIONS. You have previously been
granted options to purchase up to 190,000 shares of HNC's Common Stock at
purchase prices of between $3.00 and $32.00 per share. As of the date of this
Agreement, you have exercised 40,000 of these options. Assuming no additional
exercise of these options by you prior to the Termination Date, and assuming
your continuous employment with HNC through the Termination Date, on the
Termination Date you will have vested and unexercised interests in options to
purchase up to 119,000 shares of HNC Common Stock and you will have 31,000
unvested HNC stock options. In addition, you have been granted options to
purchase up to 40,000 shares of the Common Stock of eHNC under the eHNC Stock
Option Plan. On your date of termination, none of these eHNC options will be
vested.

         (b) CONTINUED STOCK OPTION VESTING. In accordance with the terms of
your current HNC and eHNC stock options, your stock option vesting (for both
your HNC stock options and your eHNC stock options) will continue to vest
through December 31, 2000 so long as you (a)


<PAGE>


continue to comply with your obligations under paragraph 4 below, (b) have not
violated the provisions of paragraph 9 of this Agreement relating to
non-competition, and (c) have not violated the provisions of paragraph 10 of
this Agreement relating to non-solicitation. If you have violated the provisions
of either paragraph 9 or paragraph 10 of this Agreement, or have ceased to make
yourself available to provide advice and counsel to HNC or eHNC as provided in
paragraph 4 of this Agreement, then your stock option vesting (for both HNC
stock options and eHNC stock options) will immediately terminate and you will
then be deemed, for purposes of your stock options, to have "Terminated" and
ceased to provide services to HNC and eHNC.

         (c) ACKNOWLEDGEMENT OF CONVERSION OF INCENTIVE STOCK OPTIONS. You
understand and agree that any and all HNC options you hold that are Incentive
Stock Options ("ISOS") shall become non-qualified stock options effective ninety
(90) days after the Termination Date, and that this conversion will have certain
tax ramifications for you. You understand and agree that it is your
responsibility to confer with your own personal tax advisor concerning the
conversion of your stock options.

         (d) ACCELERATION OF STOCK OPTION VESTING. HNC and eHNC agree that if,
on or before December 31, 2000 (a) you have not violated the provisions of
paragraph 4 below, (b) you have not violated the provisions of paragraph 9 of
this Agreement relating to non-competition, and (c) you have not violated the
provisions of paragraph 10 of this Agreement relating to non-solicitation, then
all unvested HNC stock options and all unvested eHNC stock options,
respectively, that you hold as of December 31, 2000 will accelerate and vest in
full on December 31, 2000 so that all of such stock options may then be
exercised in full by you. In addition, if you become unable to perform your
obligations under paragraph 4 below due to your death or disability prior to
December 31, 2000, then HNC and eHNC further agree that all unvested HNC stock
options and all unvested eHNC stock options, respectively, that you hold as of
the date of your death or disability ("TRIGGER DATE") will accelerate and vest
in full on such Trigger Date so that all of such stock options may then be
exercised in full by you (or your heirs).

         (e) ADJUSTMENT. If HNC's Board of Directors elects to generally adjust
HNC stock options to reflect any extraordinary transaction, such as a
distribution of HNC's shares of Retek Inc., your HNC stock options, if then
still in effect, would be likewise adjusted.

4. CONSULTING AND SERVICE. You agree that from the Termination Date through
December 31, 2000, you will make yourself available to provide, and will, as an
independent contractor, provide advice and counsel to HNC and eHNC for up to 30
hours per month. It is agreed by us that your provision of advice and counsel to
HNC and eHNC and your agreement make yourself available to provide continued
service to HNC and eHNC as an independent contractor will constitute "providing
services" to HNC and eHNC within the meaning of their respective stock option
plans. You will have no right to continue to provide services to HNC or eHNC
after December 31, 2000 unless HNC or eHNC, as applicable, agree to retain your
services after that date.

5. SALARY CONTINUATION: In consideration for your execution of this Agreement,
your agreement to provide advice and counsel to HNC and the general release
given by you herein, HNC agrees to pay you a monthly severance benefit in the
form of salary continuation, which you are not otherwise entitled to receive. If
you execute this Agreement and do not revoke it as specified in paragraph 24 of
this Agreement, you will receive monthly salary continuation in an amount equal
to your current monthly base salary, until the earlier of the following: (i)
December 31, 2000, or (ii) such time as you may violate the provisions of either
paragraph 4, paragraph 9 or paragraph 10 of this Agreement. You agree with HNC
that HNC may make tax


<PAGE>


and other withholding deductions that it determines in good faith are required
under applicable law with respect to any payments made by HNC under this
paragraph 5.

6. GROUP HEALTH BENEFITS. HNC will continue to maintain and pay for your and
your spouse's participation in its group medical, dental, and vision insurance
plans, until the earlier of the following: (i) December 31, 2000, or (ii) such
time as you may violate either paragraph 9 or paragraph 10 of this Agreement.
You will be eligible to continue coverage under COBRA thereafter.

7. RETURN OF HNC PROPERTY: During the period in which you are receiving salary
continuation, you will be allowed to retain the computer system currently in
your possession and will continue to have access to HNC's voice mail and
electronic mail systems. You agree, however, that at the time that salary
continuation terminates (as described in paragraph 5 hereof), you will promptly
return the computer to HNC, and that your access to HNC's voice mail and
electronic mail systems will terminate unless other agreements are reached with
HNC. You represent that as of the Termination Date, you will have returned to
HNC all other HNC property or data that was in your possession or control.

8. OTHER ACTIVITIES. It is agreed that while you are receiving salary
continuation under paragraph 5 of this Agreement, you may accept and engage in
other employment and/or consulting, and may provide service (including but not
limited to sitting as a member of another company's board of directors) to other
persons or companies, PROVIDED that such employment, consulting work or service
provision is not for any person or entity which competes in any way with the
business of HNC or any of its subsidiaries.

9. NON-COMPETITION. It is specifically understood and agreed that during the
period of time in which you are receiving salary continuation from HNC under
paragraph 5 hereof, you shall not provide services or advice to any person or
entity which competes in any way with the business of HNC or any of its business
units or subsidiaries, regardless of whether you receive compensation from such
person or entity.

10. NON-SOLICITATION. It is specifically understood and agreed that during any
period of time in which you are receiving salary continuation from HNC under
paragraph 5 hereof, you shall not, directly or indirectly, solicit or induce any
of the employees, independent contractors or agents of HNC or any of its
subsidiaries to end or reduce their relationships with or services to HNC or any
of its subsidiaries, nor shall you solicit, recruit or otherwise induce any such
person to perform services for you or for any other person or entity. The
foregoing non-solicitation obligation extends to all employees, independent
contractors and agents of HNC and all HNC's subsidiaries, business units and/or
divisions. It is understood and agreed by you and HNC that if you are a member
of another company's board of directors and that company is soliciting or
recruiting employees of HNC or any of its subsidiaries, independent contractors
or agents, it shall not be presumed that you have violated this paragraph 10,
and any such claim shall be subject to proof thereof.

11. CONFIDENTIAL INFORMATION: You acknowledge that you are bound by the attached
Invention Assignment and Proprietary Information Agreement with HNC dated
February 27, 1995, that as a result of your employment with HNC you have had
access to HNC's Confidential Information (as defined in such agreement), that
you will hold all Confidential Information in strictest confidence and that you
may not use such Confidential Information on behalf of any third party. You
confirm that you have delivered to HNC all documents and data containing or
pertaining to Confidential Information and that you have not taken with you any
such documents


<PAGE>


or data or any reproduction thereof (except as such are contained in the
computer and electronic systems referenced in paragraph 7).

12. GENERAL RELEASE. As of the date of execution of this Agreement, you, for
yourself, your heirs, executors, administrators, assigns and successors, fully
and forever release and discharge HNC and each of its current, former and future
parents, subsidiaries, related entities, employee benefit plans and their
fiduciaries, predecessors, successors, officers, directors, shareholders,
agents, employees and assigns (collectively, "RELEASEES"), with respect to any
and all claims, liabilities and causes of action, of every nature, kind and
description, in law, equity or otherwise, which have arisen, occurred or existed
at any time prior to the signing of this Agreement, including, without
limitation, any and all claims, liabilities and causes of action arising out of
or relating to your employment with HNC or the termination of your employment
with HNC.

13. KNOWING WAIVER OF EMPLOYMENT-RELATED CLAIMS. You understand and agree that,
with the exception of potential employment-related claims identified below, you
are waiving any and all rights you may have had, now have, or in the future may
have, to pursue against any of the Releasees any and all remedies available to
you under any employment-related causes of action, including without limitation,
claims of wrongful discharge, breach of contract, breach of the covenant of good
faith and fair dealing, fraud, violation of public policy, breach of privacy
rights, defamation, discrimination, personal injury, physical injury, emotional
distress, claims under Title VII of the Civil Rights Act of 1964, as amended,
the Age Discrimination in Employment Act, the Older Workers Benefit Protection
Act, the Americans With Disabilities Act, the Federal Rehabilitation Act, the
Family and Medical Leave Act, the California Fair Employment and Housing Act,
the California Family Rights Act, the Equal Pay Act of 1963, the provisions of
the California Labor Code and any other federal, state or local laws and
regulations relating to employment, conditions of employment (including wage and
hour laws) and/or employment discrimination. Claims not covered by the release
provisions of this Agreement are (i) claims for unemployment insurance benefits,
and (ii) claims under the California Workers' Compensation Act.

14. WAIVER OF CIVIL CODE Section 1542. You expressly waive any and all rights
and benefits conferred upon you by Section 1542 of the Civil Code of the State
of California, which states as follows:

         "A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE CREDITOR DOES
         NOT KNOW OR SUSPECT TO EXIST IN HIS FAVOR AT THE TIME OF EXECUTING THE
         RELEASE, WHICH IF KNOWN BY HIM MUST HAVE MATERIALLY AFFECTED HIS
         SETTLEMENT WITH THE DEBTOR."

You agree and understand that the Release given by you pursuant to this
Agreement applies to all unknown, unsuspected and unanticipated claims,
liabilities and causes of action which you may have against HNC or any of the
other Releasees.

15. SEVERABILITY OF RELEASE PROVISIONS. You agree that if any provision of the
release given by you under this Agreement is found to be unenforceable, it will
not affect the enforceability of the remaining provisions and any court of
competent jurisdiction may enforce all remaining provisions to the extent
permitted by law.

16. NONDISPARAGEMENT: You agree that you will not disparage, in writing or
orally, HNC any of its subsidiaries, or any of their products, services,
representatives, directors, officers, attorneys, successors or assigns, or any
person acting by, through, under or in concert with any of them. HNC agrees that
it will take reasonable steps to ensure that persons affiliated with HNC do not
disparage you, in writing or orally.


<PAGE>


17. LEGAL AND EQUITABLE REMEDIES: You agree that HNC will have the right to
enforce this Agreement and any of its provisions by injunction, specific
performance or other equitable remedies without prejudice to any other rights or
remedies HNC may have at law or in equity for breach of this Agreement.

18. ATTORNEY'S FEES: If any action at law or in equity is brought to enforce the
terms of this Agreement, the prevailing party will be entitled to recover its
reasonable attorneys' fees, costs and expenses from the other party, in addition
to any other relief to which such prevailing party may be entitled.

19. CONFIDENTIALITY: You agree to keep the contents, terms and conditions of
this Agreement confidential and will not disclose any information related to
this Agreement to anyone except your attorney or pursuant to a subpoena or court
order. Any breach of this confidentiality provision will be deemed to be a
material breach of this Agreement. However, HNC shall be entitled to disclose
the contents, terms and conditions of this Agreement to the extent that it has
been advised by counsel that it is required to do so under applicable law or the
rules or regulations of any securities exchange or stock quotation system on
which HNC's stock or other securities are traded or quoted.

20. NO ADMISSION OF LIABILITY: This Agreement is not, and you may not construe
or contend it to be, an admission or evidence of wrongdoing or liability on the
part of HNC, its representatives, attorneys, agents, officers, shareholders,
directors, employees, subsidiaries, successors or assigns. This Agreement will
be given the maximum protection allowable under California Evidence Code Section
1152 and/or any other state or Federal provisions of similar effect.

21. ENTIRE AGREEMENT: This Agreement constitutes the entire agreement between
you and HNC with respect to the subject matter of this document. It supersedes
all prior negotiations and agreements, written or oral, relating to this subject
matter. You acknowledge that neither HNC nor its agents or attorneys have
promised or represented, either expressly or impliedly, in writing or orally,
anything not contained in this Agreement for the purpose of inducing you to
execute this Agreement. You acknowledge that you have signed this Agreement
relying only on the promises, representations and warranties contained in this
document.

22. MODIFICATION: This Agreement may not be amended or modified in any respect
except by another written agreement that specifically refers to this Agreement,
executed by an authorized representative of each of the parties.

23. PERIOD TO REVIEW AGREEMENT. You acknowledge that this Agreement was
presented to you on December 13, 1999, and that you are entitled to have up to
twenty-one (21) days within which to review its terms. You acknowledge that you
have been advised to consult with an attorney prior to executing this Agreement.
You further represent that if you sign this Agreement before the expiration of
the twenty-one (21) day period, you voluntarily waive any remaining time period
to review and consider this Agreement.

24. REVOCATION OF AGREEMENT. You understand that you may revoke your agreement
within seven (7) days of your execution of this document. Any such revocation
must be in writing, and must be received by HNC within such seven (7) day
period. Any written revocation should be delivered to: President, HNC Software
Inc. 5935 Cornerstone Court West, San Diego, CA


<PAGE>


92121. You understand that the benefits to be provided to you under this
Agreement will be provided only after the revocation period has expired and you
have not revoked this Agreement.

25. SECTION 16 COMPLIANCE. You acknowledge that you alone are responsible for
your compliance with Section 16 under the Securities Exchange Act of 1934, as
amended, and all regulations thereunder.

If you agree to the terms of this Agreement, please sign the attached copy and
return it to me on or before January 4, 2000. PLEASE REVIEW THIS AGREEMENT
CAREFULLY. THIS AGREEMENT CONTAINS A WAIVER OF KNOWN AND UNKNOWN CLAIMS.


Very truly yours,


HNC SOFTWARE INC.                             As to paragraphs 1, 3 and 4 only
                                              eHNC INC.

By:                                           By:
   ---------------------------------              ----------------------------
       Robert North, CEO                             Robert North, CEO


READ, UNDERSTOOD AND AGREED



  /s/ Raymond V. Thomas
------------------------------------
Raymond V. Thomas