<PAGE>   1
                                                                 Exhibit 10.1.20
                                    AGREEMENT

Conseco, Inc. ("Company") and Stephen C. Hilbert ("Executive") for good and
valuable consideration the receipt and sufficiency of which are hereby
acknowledged have entered into this agreement as of April 28, 2000.

                                    Recitals

A.   Company and Executive are parties to an Employment Agreement dated as of
     January 1, 1998 and amended and restated from time to time thereafter
     including April 6, 2000 (the "Employment Agreement").

B.   The parties wish to effect a termination of Executive's employment and to
     provide for Executive's resignation of his positions with the Company and
     its affiliates.

C.   Capitalized terms not defined herein have the meanings ascribed in the
     Employment Agreement.

D.   Prior to termination of Executive's employment hereunder, Company has
     granted to Executive 3-year options to purchase 2 million shares of the
     Company's common stock under the Company's 1994 Stock and Incentive Plan
     and the 1997 Non-qualified Stock Option Plan with an exercise price of the
     mean of the high and the low sales prices reported on the NYSE Composite
     Stock Tape for April 27, 2000.

                                    Agreement

In consideration of the foregoing and the mutual covenants and undertakings
contained herein the parties agree as follows:

1.   The parties agree that the Executive's employment is terminated effective
     as of April 28, 2000 (the "Termination Date") and that their rights and
     obligations are and will be fixed as though the Company terminated the
     Executive's employment pursuant to Section 9(a) of the Employment Agreement
     and such termination is not a "Control Termination."

2.   Pursuant to and provided in Section 9(b) of the Employment Agreement the
     Company will make a severance distribution to Executive on or before May 8,
     2000 (the "Distribution Date") of (i) the Note, the Debt, and the
     Collateral Documents and (ii) $49,382,165 minus additional interest
     accruing at the rate of $5,356.16 per day from the Termination Date to the
     Distribution Date less any withholding that the Company is required to
     make.

3.   Company will pay Executive a bonus pursuant to Section 5(b)(vi) of the
     Employment Agreement that has accrued with respect to his first quarter of
     fiscal year 2000 (his "First Quarter Payment"). However, if the First
     Quarter Payment exceeds 25% of the Maximum Bonus payable with respect to
     the entire fiscal year had Executive been employed for the full year,
     Executive shall repay to the Company the excess.


<PAGE>   2



4.   Executive hereby resigns all of his offices and positions as a director,
     member or trustee with the Company and all of its subsidiaries, affiliates
     and employee benefit plans or trusts.

5.   The parties have contemporaneously entered into a Consulting Agreement
     providing, among other things, that Executive will be available to perform
     specified services during a three year term.

6.   The existing rights of Executive and obligations of Company with regard to
     indemnification of Executive that are not dependent upon Executive's
     continued employment or holding an office or directorship with the Company
     and indemnification rights under Company's current by-laws shall continue
     and will not be amended to the prejudice of Executive's rights and
     Company's obligations thereunder.

7.   With regard to stock purchases before the Termination Date made by
     Executive under the Company's Director and Officer Stock Purchase Plans
     during the term of the Consulting Agreement the Company will continue to
     treat Executive as though he were an employee/participant for purposes of
     the Company's Director and Officer Stock Purchase Plans and the Company's
     established practices and accommodations in connection therewith including
     waivers of any guarantee fees and advancement of any interest payments due.

8.   The Company agrees that it will use reasonable efforts to cause Executive
     to be included at all times as an insured at the Company's cost under
     Company officer and director liability insurance with regard to any acts,
     actions, facts, circumstances, errors or omissions performed or occurring
     prior to the Termination Date.

9.   The Company and Executive will continue to honor their existing contractual
     obligations to make premium payments when due in accordance with the terms
     of various split-dollar insurance agreements between the Company and
     Executive or trusts for the benefit of Executive or his family.

10.  The parties agree to execute any and all additional documents and take all
     actions reasonably required to more fully evidence or implement the intent
     of the parties expressed herein.

11.  This Agreement will be governed by the laws of the State of Indiana.

12.  This Agreement has been duly authorized by each party and constitutes a
     valid and binding obligation in accordance with its terms. This Agreement
     shall be binding upon and inure to the benefit of the parties and their
     successors in interest.

                                        CONSECO, INC.



                                        By  /s/ Thomas J. Kilian
                                           -------------------------------------
                                           Thomas J. Kilian, President


                                            /s/ Stephen C. Hilbert
                                           -------------------------------------
                                           Stephen C. Hilbert