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                                                                   EXHIBIT 10.50

                              AMENDMENT NUMBER FOUR
                                     to the
                                   INDENTURE,
             dated as of April 1, 2001, and as amended and restated
                     through and including November 25, 2003
                                     between
                         OPTION ONE OWNER TRUST 2001-1A
                                       and
                             WELLS FARGO BANK, N.A.

            This AMENDMENT NUMBER FOUR (this "Amendment") is made and is
effective as of this 16th day of April, 2004, between Option One Owner Trust
2001-1A (the "Issuer") and Wells Fargo Bank, N.A. (formerly known as Wells Fargo
Bank Minnesota, National Association), as Indenture Trustee (the "Indenture
Trustee"), to the Indenture dated as of April 1, 2001, and as amended and
restated through and including November 25, 2003 (the "Indenture"), between the
Issuer and the Indenture Trustee.

                                    RECITALS

            WHEREAS, the parties hereto desire to amend the Indenture subject to
the terms and conditions of this Amendment.

            NOW THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, and of the mutual covenants herein
contained, the parties hereto hereby agree as follows:

            SECTION 1. Defined Terms. Any terms capitalized but not otherwise
defined herein shall have the respective meanings set forth in the Indenture.

            SECTION 2. Amendment.

            (a) The Granting Clause of the Indenture is hereby amended by
deleting it in its entirety and replacing it with the following:

                                "GRANTING CLAUSE

            Subject to the terms of this Indenture, the Issuer hereby Grants on
the Closing Date, to the Indenture Trustee, as Indenture Trustee for the benefit
of the Noteholders, all of the Issuer's right, title and interest, whether now
owned or hereafter acquired, in and to: (i) such Loans as from time to time are
subject to the Sale and Servicing Agreement as listed in the Loan Schedule, as
the same may be amended or supplemented on each Transfer Date and by the removal
of Deleted Loans and Unqualified Loans and by the addition of Qualified
Substitute Loans, together with the Servicer's Loan Files and the Custodial Loan
Files relating thereto and all proceeds thereof, (ii) the Mortgages and security
interests in the Mortgaged Properties, (iii) all payments in respect of interest
and principal with respect to each Loan and Residual Security received on or
after the related Transfer Cut-off Date, (iv) such assets as from time to time
are identified as Foreclosure Property,

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(v) such assets and funds as are from time to time deposited in the Distribution
Account, Collection Account and the Transfer Obligation Account, including,
without limitation, amounts on deposit in such accounts that are invested in
Permitted Investments, (vi) lenders' rights under all Mortgage Insurance
Policies and to any Mortgage Insurance Proceeds, (vii) Net Liquidation Proceeds
and Released Mortgaged Property Proceeds, (viii) all right, title and interest
of the Trust (but none of the obligations) in and to the obligations of Hedging
Counterparties under Hedging Instruments; (ix) all right, title and interest of
each of the Depositor, the Loan Originator and the Trust in and under the Basic
Documents including, without limitation, the obligations of the Loan Originator
under the Loan Purchase and Contribution Agreement, the Master Disposition
Confirmation Agreement and the Residual Securities Transfer Agreement, and all
proceeds of any of the foregoing, (x) all right, title and interest of the
Issuer in and to the Sale and Servicing Agreement, including the Issuer's right
to cause the Loan Originator to repurchase Loans and Residual Securities from
the Issuer under certain circumstances described therein), (xi) all right, title
and interest (but none of the obligations) of the Trust in, to and under the
Advance Note and all Additional Note Balances thereunder, (xii) all right, title
and interest (but none of the obligations) of the Trust in, to and under the
Advance Documents, (xiii) such Residual Securities as from time to time are
subject to this Agreement as listed in the Residual Securities Schedule, as the
same may be amended or supplemented on each Transfer Date and by the removal of
Deleted Residual Securities and Unqualified Residual Securities and by the
addition of Qualified Substitute Residual Securities, together with the Loan
Documents relating thereto and all proceeds thereof, (xiv) all other Property of
the Trust from time to time and (xv) all present and future claims, demands,
causes of action and choses in action in respect of any or all of the foregoing
and all payments on or under and all proceeds of every kind and nature
whatsoever in respect of any or all of the foregoing, including all proceeds of
the conversion thereof, voluntary or involuntary, into cash or other liquid
property, all cash proceeds, accounts, accounts receivable, notes, drafts,
acceptances, chattel paper, checks, deposit accounts, insurance proceeds,
condemnation awards, rights to payment of any and every kind and other forms of
obligations and receivables, instruments and other property which at any time
constitute all or part of or are included in the proceeds of any of the
foregoing (collectively, the "Collateral").

            The foregoing Grant is made in trust to secure the payment of
principal of and interest on, and any other amounts owing in respect of, the
Notes, and to secure compliance with the provisions of this Indenture, all as
provided in this Indenture.

            The Indenture Trustee, as Indenture Trustee on behalf of the
Noteholders, acknowledges such Grant, accepts the trusts hereunder and agrees to
perform its duties required in this Indenture to the best of its ability to the
end that the interests of the Noteholders may adequately and effectively be
protected."

            (b) Section 1.01 of the Indenture is hereby amended by adding the
following definition:

            "Residual Security" Any security sold to the Trust hereunder and
pledged to the Indenture Trustee, which security must be (i) a mortgage-backed
security issued by Option One Mortgage Acceptance Corp. and evidencing an
interest in a securitization trust backed by residential mortgage loans, which
mortgage loans are serviced by Option One Mortgage Corporation (in such

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capacity, "Option One") (including, without limitation, securities designated as
class C certificates and class P certificates that meet the foregoing criteria)
or (ii) a net interest margin security issued by a trust sponsored by Option One
and backed by class C certificates and/or Class P certificates, which
certificates are in turn backed by residential mortgage loans serviced by Option
One."

            (c) Section 1.01 of the Indenture is hereby amended by deleting the
definition of "Maturity Date" in its entirety and replacing it with the
following definition:

            "Maturity Date: means, with respect to the Notes, April 30, 2004."

            (d) Section 2.08(e)(ii) of the Indenture is hereby amended by
deleting such subsection it in its entirety and replacing it with the following:

            "(ii) the Issuer is the owner of all of the Loans and the Residual
Securities, has not assigned any interest or participation in the Loans or the
Residual Securities (or, if any such interest or participation has been
assigned, it has been released) and has the right to Grant all of the Loans and
the Residual Securities to the Indenture Trustee;"

            (e) Section 3.08 of the Indenture is hereby amended by deleting such
section in its entirety and replacing it with the following:

            "Section 3.08. Assignment of Rights. The Issuer grants and assigns
to the Initial Noteholder for the benefit of the Secured Parties all rights of
the Issuer to enforce the covenants and conditions set forth in the Advance
Note, the Advance Documents, the Residual Securities and the Loan Documents
relating to the Residual Securities and all voting rights and rights of the
Issuer to give any waivers or consents required or allowed under the Advance
Note, the Advance Documents and the Loan Documents relating to the Residual
Securities, and such waivers and consents shall be binding upon the Issuer as if
the Issuer had given the same. The Issuer hereby constitutes and irrevocably
appoints the Initial Noteholder, with full power of substitution and revocation,
as the Issuer's true and lawful agent and attorney-in-fact, with the power to
the full extent permitted by law, to affix to any certificates and documents
representing the Advance Note or any Residual Security the endorsements
delivered with respect thereto, and to transfer or cause the transfer of the
Advance Note and each Residual Security, or any part thereof, on the books of
the Advance Trust or the issuer of such Residual Security, as applicable, to the
name of the Indenture Trustee on behalf of the Secured Parties or any nominee of
hereof, and thereafter to exercise with respect to such Advance Note or Residual
Security, all the rights, powers and remedies of an owner. The power of attorney
granted pursuant to this Indenture and all authority hereby conferred are
granted and conferred solely to protect the Secured Parties respective interest
in the Collateral and shall not impose any duty upon the Initial Noteholder to
exercise any power. The Issuer shall execute any documentation including,
without limitation, any powers of attorney and/or irrevocable proxies, requested
by the Initial Noteholder to effectuate such assignment. The Issuer shall, or
shall cause the Receivables Seller and the Loan Originator (as applicable) to,
provide the Initial Noteholder with copies of all reports, notices, statements
and certificates delivered under the Advance Documents or the Loan Documents
relating to the Residual Securities, and any other information that the Initial
Noteholder shall reasonably request. Delivery of such reports, notices,
information and documents to the Initial Noteholder under this section is for
informational purposes only and the Initial Noteholders's receipt

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of such shall not constitute constructive notice of any information contained
therein or determinable from information contained therein, including the
Issuer's compliance with any of its covenants. The foregoing grant and
assignment are powers coupled with an interest and are irrevocable."

            (f) Section 7.03 of the Indenture is hereby amended by deleting such
section in its entirety and replacing it with the following:

            "Section 7.03. 144A Information. The Indenture Trustee, to the
extent it has any such information in its possession, shall provide to any
Noteholder and any prospective transferee designated by any such Noteholder
information regarding the Notes, the Loans, the Residual Securities and such
other information as shall be necessary to satisfy the condition to eligibility
set forth in Rule 144A(d)(4) under the Securities Act for transfer of any such
Note without registration thereof under the Securities Act pursuant to the
registration exemption provided by Rule 144A under the Securities Act."

            (g) The seventh paragraph of Exhibit A to the Indenture is hereby
amended by deleting such paragraph in its entirety and replacing it with the
following:

            "The Servicer may, at its option, effect an early redemption of the
Notes for an amount equal to the Note Redemption Amount on any Payment Date on
or after the Clean-up Call Date. The Servicer shall effect such early
termination by providing notice thereof to the Indenture Trustee and Owner
Trustee and by purchasing all of the Loans and the Residual Securities at a
purchase price, payable in cash, equal to the Termination Price."

            SECTION 3. Representations. In order to induce the parties hereto to
execute and deliver this Amendment, the Issuer hereby represents to the
Indenture Trustee and the Noteholders that as of the date hereof, after giving
effect to this Amendment, (a) all of its respective representations and
warranties in the Indenture and the other Basic Documents are true and correct,
and (b) it is otherwise in full compliance with all of the terms and conditions
of the Indenture.

            SECTION 4. Limited Effect. Except as expressly amended and modified
by this Amendment, the Indenture shall continue in full force and effect in
accordance with its terms. Reference to this Amendment need not be made in the
Indenture or any other instrument or document executed in connection therewith
or herewith, or in any certificate, letter or communication issued or made
pursuant to, or with respect to, the Indenture, any reference in any of such
items to the Indenture being sufficient to refer to the Indenture as amended
hereby.

            SECTION 5. Fees and Expenses. The Issuer covenants to pay as and
when billed by the Initial Noteholder all of the reasonable out-of-pocket costs
and expenses incurred in connection with the transactions contemplated hereby
and in the other Basic Documents including, without limitation, (i) all
reasonable fees, disbursements and expenses of counsel to the Initial Noteholder
and (ii) all reasonable fees and expenses of the Indenture Trustee and its
counsel.

            SECTION 6. Governing Law. THIS AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD
TO THE CONFLICT OF LAWS DOCTRINE APPLIED IN SUCH STATE.

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            SECTION 7. Counterparts. This Amendment may be executed by each of
the parties hereto on any number of separate counterparts, each of which shall
be an original and all of which taken together shall constitute one and the same
instrument.

            SECTION 8. Limitation on Liability. It is expressly understood and
agreed by the parties hereto that (a) this Amendment is executed and delivered
by Wilmington Trust Company, not individually or personally, but solely as Owner
Trustee of Option One Owner Trust 2001-1A in the exercise of the powers and
authority conferred and vested in it, (b) each of the representations,
undertakings and agreements herein made on the part of the Issuer is made and
intended not as personal representations, undertakings and agreements by
Wilmington Trust Company but is made and intended for the purpose for binding
only the Issuer, (c) nothing herein contained shall be construed as creating any
liability on Wilmington Trust Company, individually or personally, to perform
any covenant either expressed or implied contained herein, all such liability,
if any, being expressly waived by the parties hereto and by any Person claiming
by, through or under the parties hereto and (d) under no circumstances shall
Wilmington Trust Company be personally liable for the payment of any
indebtedness or expenses of the Issuer or be liable for the breach or failure of
any obligation, representation, warranty or covenant made or undertaken by the
Issuer under this Amendment or any other related documents.

                            [signature page follows]

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            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed and delivered by their duly authorized officers as of the day and
year first above written.

                                OPTION ONE OWNER TRUST 2001-1A

                                By: Wilmington Trust Company, not in its
                                individual capacity but solely as owner trustee

                                By: /s/ Rachel L. Simpson
                                    --------------------------------------------
                                Name: Rachel L. Simpson
                                Title: Financial Services Officer

                                WELLS FARGO BANK, N.A., as Indenture Trustee

                                By: /s/ REID DENNY
                                    --------------------------------------------
                                Name: REID DENNY
                                Title: VICE PRESIDENT