Widow Jane Keller is owner of an island in the middle of a river near Los Angeles. She is selling the island to millionaire Parker Benton, to build his new home. The island had an oil lease against it, which had apparently expired for non-payment. Promoter Scott Shelby tries to pay the back lease payments to reinstate the lease, but there is a legal question whether he can do so. Parker Benton would prefer to buy the island free and clear, so invites all the parties - including Perry Mason, representing Jane - for a cruise on his yacht to sit down and try to come to a friendly agreement.