<PAGE>

                                                                   Exhibit 10.18

                THIRD AMENDMENT TO CREDIT AND SECURITY AGREEMENT
                                      AND
                 FIRST AMENDMENT TO COLLATERAL PLEDGE AGREEMENT

        This Amendment, dated as of March 30, 2001, is made by and among
LUMINANT WORLDWIDE CORPORATION, a Delaware corporation, LWC OPERATING CORP., a
Delaware corporation, LWC MANAGEMENT CORP., a Delaware corporation, POTOMAC I
HOLDINGS, INC., a Delaware corporation, MULTIMEDIA I HOLDINGS, INC., a
Delaware corporation, RSI GROUP, INC., a Texas corporation, ALIGN SOLUTIONS
CORP., a Delaware corporation, POTOMAC PARTNERS MANAGEMENT CONSULTING, LLC, a
Delaware limited liability company, MULTIMEDIA RESOURCES, LLC, a New York
limited liability company, INTERACTIVE8, INC., a New York corporation, BD
ACQUISITION CORP., a Delaware corporation, RESOURCE SOLUTIONS INTERNATIONAL,
LLC, a Texas limited liability company, INTEGRATED CONSULTING, INC., a Texas
corporation, FREE RANGE MEDIA, INC., a Washington corporation, ALIGN-FIFTH
GEAR ACQUISITION CORPORATION, a Delaware corporation, and ALIGN-SYNAPSE
ACQUISITION CORPORATION, a Texas corporation (collectively, the "Borrowers"
and each a "Borrower"), and WELLS FARGO BUSINESS CREDIT, INC., a Minnesota
corporation, (the "Lender").

                                    RECITALS

        The Borrowers and the Lender have entered into a Credit and Security
Agreement dated as of April 5, 2000 as amended by a First Amendment to Credit
and Security Agreement dated as of August 31, 2000, a letter amendment dated
as of September 21, 2000, and a Second Amendment to Credit and Security
Agreement dated as of December 28, 2000 (as amended to date, the "Credit
Agreement").

        Parent Borrower executed and delivered the Pledge Agreement on
December 28, 2000, thereby subjecting its general brokerage account no.
12624854, to which the Pledged Securities had been credited, to a security
interest in favor of the Lender.  Contemporaneously, with the consent of
Parent Borrower, the Lender notified Wells Fargo Brokerage Services, LLC (the
"Brokerage") that the account

<PAGE>

was subject to the Lender's security interest, and the Brokerage agreed to
comply with buy, sell and withdrawal orders initiated by the Lender and
permitted under the terms of the Pledge Agreement.

        The Borrowers have requested that the Lender agree to waive certain
Events of Default and that certain amendments be made to the Credit Agreement.
The Lender wishes to clarify and confirm certain matters in connection with
the Pledge Agreement.  Accordingly, the parties have agreed to amend the
Credit Agreement and the Pledge Agreement in the manner set forth herein.

        NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements herein contained, the receipt and sufficiency of
which are hereby acknowledged, it is agreed as follows:

        1.      DEFINED TERMS.  Capitalized terms used in this Amendment which
                are defined in the Credit Agreement shall have the same
                meanings as defined therein, unless otherwise defined herein.
                In addition, Section 1.1 of the Credit Agreement is amended by
                adding or amending, as the case may be, the following
                definitions:

                "`Fixed Charge Coverage' means as of any date, EBITDA LESS the
        sum of (a) principal payments on Permitted Indebtedness, (b) unfinanced
        Capital Expenditures, (c) cash payments of Contingent Consideration,
        (d) reductions in the Borrowers' reserves for bad debt, and (e)
        collections with respect to accounts receivable charged off in prior
        periods, in each case, for the calendar year-to-date period ending on
        such date on a consolidated basis."

                "`Permitted Indebtedness' means indebtedness permitted under
        Section 7.2."

                "`Pledged Securities' means those Qualified Pledged Securities
        and other securities owned by certain of the Borrowers, subject to the
        Pledge Agreement."

                "`Qualified Pledged Securities' means any securities owned by
        any Borrower that evidence obligations of the United States government
        or securities owned by the Borrowers that are rated "A-1" by Standard&
        Poors Corporation or "P-1" by Moody's Investors Service, and are
        pledged to the Lender under the Pledge Agreement."

        2.      LANDLORD LETTER OF CREDIT.  Wells Fargo Bank, National
                Association ("Wells Fargo Bank") has issued Letter of Credit
                No. NZS337627, dated November 12, 1999, in favor of 114 West
                26th Street Associates, L.P. and for the account of Parent
                Borrower (the "Existing Credit").  Parent Borrower has granted
                a security interest in its account no.11710282 to secure the
                obligation to reimburse Wells Fargo Bank for draws under the
                Existing Credit.  Parent Borrower has requested that the
                Lender cause an Issuer to issue a Letter of Credit to replace
                the Existing Credit (such new Letter of Credit being referred
                to herein as the "Landlord Letter of Credit").  The advantages
                to Parent Borrower will be (i) that the Landlord Letter of
                Credit can be in a lesser face amount than the Existing
                Credit, and (ii) that Parent Borrower will be able to
                consolidate all of its investment property into its account
                no.12624854 maintained with the Brokerage.  Accordingly, the
                Lender and Parent Borrower hereby agree to cooperate with one
                another in order to accomplish the following necessary steps
                as soon as possible, but in no event later than April30, 2001:
                 (A) obtain the agreement of 114 West 26th Street Associates,
                L.P. to accept the Landlord Letter of Credit in substitution
                for the Existing Credit; (B) cause an Issuer to issue the
                Landlord Letter of Credit; (C) cause Wells Fargo Bank to
                cancel the Existing Credit; and (D) transfer all of the
                financial assets in Parent Borrower's account no.11710282 into
                its account no.12624854 maintained with the Brokerage,
                whereupon such assets shall be subject to the security
                interest created under the Pledge Agreement.  By way of
                clarification, the Landlord Letter of Credit shall be a
                "Letter of Credit" as such term is defined in the Credit
                Agreement.

<PAGE>

        3.      AMENDMENTS TO PLEDGE AGREEMENT, ETC.  The Pledge Agreement is
                hereby amended as follows:

        (a)     The Debtor's correct name in the heading is "Luminant
        Worldwide Corporation."

        (b)     The correct description of property owned by the Debtor and
        held by the Secured Party is "General Brokerage Account at Wells Fargo
        Brokerage Services, LLC, titled Luminant Worldwide Corporation account
        #12624854, together with all rights in connection with such property
        (herein called the "Collateral")."

        (c)     Section 2(a) is hereby amended in it entirety to be and read as
        follows:

                        "(a) Debtor will join with Secured Party in taking any
                action reasonably required by Secured Party and consistent with
                the terms herein in order to perfect the Security Interest and
                protect the rights and priorities of the Secured Party with
                respect to the Collateral."

Parent Borrower hereby confirms that the existing agreement between the Lender
and the Brokerage was made with its consent, and agrees that it will, if
requested, join with the Lender in executing any instructions to or agreements
with the Brokerage in accordance with revised section 2(a) of the Pledge
Agreement.

        4.      FINANCIAL COVENANTS.  Sections 6.12, 6.13, 6.14 and 7.11 of
                the Credit Agreement are hereby amended in their entirety to
                read as follows:

                "Section 6.12 - RESERVED."
                "Section 6.13 - RESERVED."

                "Section 6.14 MINIMUM FIXED CHARGE COVERAGE.  The Borrowers
        will collectively maintain at all times during each period set forth
        below, Fixed Charge Coverage of not less than the amount set forth
        opposite such period (negative numbers are indicated by parentheses):

<TABLE>
<CAPTION>
                PERIOD                                  MINIMUM FIXED CHARGE
                                                              COVERAGE
<S>                                                     <C>
January 1, 2001 through March 30, 2001                      $(2,500,000)
March 31, 2001 through June 29, 2001                        ($3,000,000)
June 30, 2001 through September 29, 2001                    ($2,500,000)
September 30, 2001 through December 30, 2001                ($2,000,000)
December 31, 2001                                            $1,000,000
January 1, 2002 through March 30, 2002                      ($1,000,000)
March 31, 2002                                              ($1,000,000)"
</TABLE>

                "Section 7.11 CAPITAL EXPENDITURES.  The Borrowers will not
        incur or contract to incur Capital Expenditures of more than
        $4,500,000 during the fiscal year ending on December 31, 2001, and not
        more than $1,500,000 during the period from January 1, 2002 through
        March 31, 2002."

1.      ACQUISITIONS.  Section 7.8 of the Credit Agreement is amended to read
        as follows:

                "Section 7.8 CONSOLIDATION AND MERGER; ASSET ACQUISITIONS.
        Without the prior written consent of the Lender, no Borrower will, nor
        will it permit any controlled Affiliate to, consolidate with or merge
        into any Person, or permit any other Person to merge into it, or
        acquire (in a transaction analogous in purpose or effect to a
        consolidation or merger) all or substantially all the assets of any
        other Person."

<PAGE>

2.      EVENTS OF DEFAULT.  Section 8.1 of the Credit Agreement is amended by
        deleting the word "or" at the end of subjection (n), changing the
        final period in subjection (o) to "; or" and adding the following new
        subjection (p):

                "(p)    The aggregate market value of Qualified Pledged
        Securities as of the close of business on any Banking Day shall be
        less than $7,500,000 prior to issuance of the Landlord Letter of
        Credit or less than $7,800,000 upon or following issuance of the
        Landlord Letter of Credit.

7.      COMPLIANCE CERTIFICATE.  Exhibit B to the Credit Agreement is replaced
        by Exhibit A to this Amendment.

8.      NO OTHER CHANGES.  Except as explicitly amended by this Amendment, all
        of the terms and conditions of the Credit Agreement shall remain in
        full force and effect and shall apply to any advance or letter of
        credit thereunder.

9.      WAIVER OF DEFAULTS.  The Borrowers are in default of Section 6.1(b) of
        the Credit Agreement which requires the Borrowers to deliver to the
        Lender certain financial reports and a compliance certificate within
        30 days after the end of each month that is not a quarter end.  The
        Lender did not receive such reports and certificate for the month
        ended January 31, 2001, and the Borrowers have indicated to the Lender
        that the reports and certificate for the month ended February 28,
        2001, will be delivered late.  The Lender agrees to waive these Events
        of Default provided it receives all such reports before April 30,
        2001.  This waiver shall be effective only in this specific instance
        and for the specific purpose for which it is given, and this waiver
        shall not entitle the Borrowers to any other or further waiver in any
        similar or other circumstances.  As of the date hereof, the Lender has
        no knowledge of any Defaults or Events of Default other than the
        Events of Default expressly set forth herein.

10.     CONDITIONS PRECEDENT.  This Amendment, and the waiver set forth in
        Paragraph 9 hereof, shall be effective when the Lender shall have
        received an executed original hereof, together with such other matters
        as the Lender may reasonably require; provided that Lender shall
        forward to Borrowers written confirmation when all of the conditions
        precedent in this paragraph have been satisfied.

11.     REPRESENTATIONS AND WARRANTIES.  The Borrowers hereby represent and
        warrant to the Lender as follows:

(a)     The Borrowers have all requisite power and authority to execute this
        Amendment and to perform all of their obligations hereunder, and this
        Amendment has been duly executed and delivered by the Borrowers and
        constitutes the legal, valid and binding obligation of the Borrowers,
        enforceable in accordance with its terms, except as enforceability may
        be limited by applicable bankruptcy, insolvency, fraudulent
        conveyance, reorganization, moratorium or similar laws affecting
        creditors' rights generally and by general equitable principles.

<PAGE>

(b)     The execution, delivery and performance by the Borrowers of this
        Amendment have been duly authorized by all necessary corporate or
        limited liability company action and do not (i) require any
        authorization, consent or approval by any governmental department,
        commission, board, bureau, agency or instrumentality, domestic or
        foreign, (ii) violate any provision of any law, rule or regulation or
        of any order, writ, injunction or decree presently in effect, having
        applicability to the Borrowers, or the articles of incorporation,
        by-laws or comparable organizational documents of the Borrowers, or
        (iii) result in a breach of or constitute a default under any
        indenture or loan or credit agreement or any other agreement, lease or
        instrument to which any Borrower is a party or by which it or its
        properties may be bound or affected.

(c)     All of the representations and warranties contained in Article V of the
        Credit Agreement are correct in all material respects on and as of the
        date hereof as though made on and as of such date, except to the
        extent that such representations and warranties relate solely to an
        earlier date.

12.     REFERENCES.  All references in the Credit Agreement to "this
        Agreement" shall be deemed to refer to the Credit Agreement as amended
        hereby; and any and all references in the Security Documents to the
        Credit Agreement shall be deemed to refer to the Credit Agreement as
        amended hereby.

13.     NO OTHER WAIVER.  Except as set forth in Paragraph 9 hereof, the
        execution of this Amendment and acceptance of any documents related
        hereto shall not be deemed to be a waiver of any Default or Event of
        Default under the Credit Agreement or breach, default or event of
        default under any Security Document or other document held by the
        Lender, whether or not known to the Lender and whether or not existing
        on the date of this Amendment.

14.     RELEASE.  Each Borrower hereby absolutely and unconditionally releases
        and forever discharges the Lender, and any and all participants,
        parent corporations, subsidiary corporations, affiliated corporations,
        insurers, indemnitors, successors and assigns thereof, together with
        all of the present and former directors, officers, agents and
        employees of any of the foregoing, from any and all claims, demands or
        causes of action of any kind, nature or description, whether arising
        in law or equity or upon contract or tort or under any state or
        federal law or otherwise, which that Borrower has had, now has or has
        made claim to have against any such person for or by reason of any
        act, omission, matter, cause or thing whatsoever arising from the
        beginning of time to and including the date of this Amendment, whether
        such claims, demands and causes of action are matured or unmatured or
        known or unknown.

15.     COSTS AND EXPENSES.  The Borrowers hereby reaffirm their agreement
        under the Credit Agreement to pay or reimburse the Lender on demand
        for all costs and expenses incurred by the Lender in connection with
        the Credit Agreement, the Security Documents and all other documents
        contemplated thereby, including without limitation all reasonable fees
        and disbursements of legal counsel.  Without limiting the generality
        of the foregoing, the Borrowers specifically agree to pay all
        reasonable fees and disbursements of counsel to the Lender for the
        services performed by such counsel in connection with the preparation
        of this Amendment and the documents and instruments incidental hereto.
         The Borrowers hereby agree that the Lender may, at any time or from
        time to time in its sole discretion and without further authorization
        by the Borrowers, make an Advance to the Borrowers under the Credit
        Agreement, or apply the proceeds of any Advance, for the purpose of
        paying any such fees, disbursements, costs and expenses.

<PAGE>

16.     MISCELLANEOUS.  This Amendment may be executed in any number of
        counterparts, each of which when so executed and delivered shall be
        deemed an original and all of which counterparts, taken together,
        shall constitute one and the same instrument.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly
executed as of the date first written above.

WELLS FARGO BUSINESS CREDIT, INC.       LUMINANT WORLDWIDE CORPORATION

By /s/ Thomas J. Krueger                By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       Its _____________________________
   Its Vice President

LWC OPERATING CORP.                     LWC MANAGEMENT CORP.
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

POTOMAC I HOLDINGS, INC.                MULTIMEDIA I HOLDINGS, INC.
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

RSI GROUP, INC.                         ALIGN SOLUTIONS CORP.
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

POTOMAC PARTNERS MANAGEMENT             MULTIMEDIA RESOURCES, LLC
CONSULTING, LLC
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

INTERACTIVE8, INC.                      BD ACQUISITION CORP.
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

RESOURCE SOLUTIONS INTERNATIONAL, LLC   INTEGRATED CONSULTING, INC.
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

FREE RANGE MEDIA, INC.                  ALIGN-FIFTH GEAR ACQUISITION CORPORATION
By /s/ James R. Corey                   By /s/ James R. Corey
   _________________________________       _________________________________
   _________________________________       _________________________________

ALIGN-SYNAPSE ACQUISITION CORPORATION
By /s/ James R. Corey
   _________________________________
   _________________________________

<PAGE>

                                        Exhibit A to Third Amendment to
                                        Credit and Security Agreement
                                        Exhibit B to Credit and Security
                                        Agreement

                             COMPLIANCE CERTIFICATE

To:      Thomas J. Krueger
         Wells Fargo Business Credit, Inc.
Date:    __________________, 2001
Subject: Luminant Worldwide Corporation, LWC Operating Corp., LWC Management
         Corp., Potomac I Holdings, Inc., Multimedia I Holdings, Inc., RSI
         Group, Inc., Align Solutions Corp., Potomac Partners Management
         Consulting, LLC, Multimedia Resources, LLC, Interactive8, Inc., BD
         Acquisition Corp., Resource Solutions International, LLC, Integrated
         Consulting, Inc., Free Range Media, Inc., Align-Fifth Gear Acquisition
         Corporation, and Align-Synapse Acquisition Corporation

                Financial Statements

        In accordance with our Credit and Security Agreement dated as of April
5, 2000, as amended (as amended, the "Credit Agreement"), attached are the
consolidated financial statements of Luminant Worldwide Corporation (the
"Parent Borrower") as of and for ________________, 200__ (the "Reporting
Date") and the year-to-date period then ended (the "Current Financials"). All
terms used in this certificate have the meanings given in the Credit Agreement.

        I certify that the Current Financials have been prepared in accordance
with GAAP, subject to year-end audit adjustments (and with respect to all
Current Financials which are interim financials, except for the absence of
footnotes), and fairly present the Borrowers' financial condition and the
results of its operations as of the date thereof.

                EVENTS OF DEFAULT. (Check one):

        / /     The undersigned does not have knowledge of the occurrence of a
                Default or Event of Default under the Credit Agreement.
        / /     The undersigned has knowledge of the occurrence of a Default
                or Event of Default under the Credit Agreement not previously
                reported in writing to the Lender and attached hereto is a
                statement of the facts with respect to thereto. The Borrowers
                acknowledge that pursuant to Section 2.13(d) the Lender may
                impose the Default Rate at any time during the resulting Default
                Period.

                FINANCIAL COVENANTS.  I further hereby certify as follows:

        1.      MINIMUM FIXED CHARGE COVERAGE.  Pursuant to Section 6.14 of
                the Credit Agreement, for the year-to-date period ending on the
                Reporting Date, the Borrowers' Fixed Charge Coverage was
                $_______________ which satisfies does not satisfy the
                requirement that such amount be not less than $________________
                for such period as set forth in the table below (negative
                numbers are indicated by parentheses):

<PAGE>

<TABLE>
<CAPTION>
                PERIOD                                  MINIMUM FIXED CHARGE
                                                              COVERAGE
<S>                                                     <C>
January 1, 2001 through March 30, 2001                        $(2,500,000)
March 31, 2001 through June 29, 2001                          ($3,000,000)
June 30, 2001 through September 29, 2001                      ($2,500,000)
September 30, 2001 through December 30, 2001                  ($2,000,000)
December 31, 2001                                              $1,000,000
January 1, 2002 through March 30, 2002                        ($1,000,000)
March 31, 2002                                                ($1,000,000)"
</TABLE>


        2.      CAPITAL EXPENDITURES.  Pursuant to Section 7.11 of the Credit
                Agreement, for the year-to-date period ending on the Reporting
                Date, the Borrowers have expended or contracted to expend for
                Capital Expenditures, $__________________ in the aggregate
                which satisfies does not satisfy the requirement that such
                expenditures not exceed $4,500,000 in the aggregate during the
                fiscal year ending December 31, 2001, or $1,500,000 in the
                aggregate during the period from January 1, 2002 to March 31,
                2002.

Attached hereto are all relevant facts in reasonable detail to evidence, and
the computations of the financial covenants referred to above.  These
computations were made in accordance with GAAP.

                                        LUMINANT WORLDWIDE CORPORATION

                                        By ____________________________
                                           Its Chief Financial Officer