Successful attorney Phil Carlyle, 42, plans to run out on his wife Dorsey, 47 and away with his mistress Diane Stewart, 28, and decides to stage his own "death" as a cover. He persuades friend Mike Hartney, 35, to sail his cabin cruiser which he has time-bombed and spread with his personal identification papers; after the explosion, it is assumed "Phil Carlyle" is dead.Julie Barton, 25, hires Barnaby to find her missing lover, Mike, and Jones tracks down another of Mike's old girlfriends, Diane Stewart, who is living in isolation with "Fred Williams" (Phil Carlyle).When Jones intrudes on their idyll and seems to guess their ruse, Diane panícs and Phil strangles her, Barnaby visits their cabin and accuses "Fred Williams" of being Phil Carlyle. Phil confesses and is about to kill Baraaby, who cleverly foils him and turns him in to the police.