Travis McGee Rod Taylor and his close friend Meyer Theodore Bikel are fishing beneath a bridge in their coastal Florida home when a shocking sight upends their quiet day: a young woman is hurled into the water, bound and weighted at the ankles with a dumbbell. Travis dives in to pull her to safety, and she introduces herself as Vangie Suzy Kendall. He is surprised when she insists that he not contact the police, and he finds himself slowly drawn to the enigmatic woman.
She gradually opens up, confessing that she barely escaped death because of her involvement in a prostitution ring and a murder scheme. Vangie reveals that she was part of a coordinated team that operated on cruise ships, pairing pretty young women with a male partner to lure rich, lonely men, drug their drinks, and rob them. The male partner in this deadly scheme is a sadistic bodybuilder named Terry William Smith, who throws the drugged men overboard to drown. Vangie’s safety is compromised after she objects to the murders, having been led to believe the men would simply be robbed, not killed.
Despite Travis and Meyer’s efforts to shield Vangie, Terry tracks her down and murders her, forcing the pair to take action. They vow to dismantle the gang and begin an investigative pursuit that leads them to Merrimay, a woman who bears a striking resemblance to Vangie. On a cruise ship, Travis poses as a wealthy man traveling alone, serving as bait for Terry and his new partner Del Ahna Capri. Del approaches Travis and invites him to her room, but knowing the scheme, he refuses the drinks she serves and warns that her life is in danger.
Angry that their operation has been uncovered, Terry, who lies in wait in an adjoining room, savagely attacks Travis and leaves him wounded. Terry then flees the cruise ship, where Meyer and Merrimay wait at the pier. Merrimay, her hair dyed to resemble Vangie, calls out to Terry, who, bloodied from his earlier fight, goes berserk at the idea that Vangie survived and storms down the gangplank toward her, pushing aside anyone who gets in his way. Security guards try to stop him, but they only slow him down until Travis arrives and incapacitates the massive killer with a decisive blow from a wooden 2x4.
The pursuit culminates on Travis’s houseboat, The Busted Flush, where Merrimay sits down with him for a quiet talk. She asks if he still loves Vangie and hints at a possible future together, but McGee, ever thoughtful, replies that he will need time to decide whether he is ready to welcome a new love into his life.
