Exhibit 99.1
                                                                    ------------

                             JOINT FILING AGREEMENT
                          PURSUANT TO RULE 13d-1(k)(1)
                          ----------------------------

     The undersigned acknowledge and agree that the foregoing statement on
Schedule 13G is filed on behalf of each of the undersigned and that all
subsequent amendments to this statement on Schedule 13G shall be filed on behalf
of each of the undersigned without the necessity of filing additional joint
filing agreements. The undersigned acknowledge that each shall be responsible
for the timely filing of such amendments, and for the completeness and accuracy
of the information concerning it contained therein, but shall not be responsible
for the completeness and accuracy of the information concerning the others,
except to the extent that it knows or has reason to believe that such
information is inaccurate. This Agreement may be executed in any number of
counterparts and all of such counterparts taken together shall constitute one
and the same instrument.


Dated: July 20, 2004


                                        ROCKBAY CAPITAL MANAGEMENT, LP

                                        By: Rockbay Capital Advisors, Inc.,
                                            its general partner

                                        By: /s/ Atul Khanna
                                            ------------------------------
                                            Name:  Atul Khanna
                                            Title: Chief Executive Officer


                                        ROCKBAY CAPITAL ADVISORS, INC.

                                        By: /s/ Atul Khanna
                                            ------------------------------
                                            Name:  Atul Khanna
                                            Title: Chief Executive Officer


                                        /s/ Atul Khanna
                                        ------------------------------
                                        Atul Khanna


                                        /s/ Jonathan Baron
                                        ------------------------------
                                        Jonathan Baron




                     [JOINT FILING AGREEMENT OF SCHEDULE 13G
                     WITH RESPECT TO PLAINS RESOURCES INC.]