It is summer, and obsessed Ralph Gordon stalks a high-school teacher, 28-year-old Diane Marshall. He watches her from an old warehouse while she is relaxing in her swimsuit on one of the boats. One of Diane's students, 18-year-old Sean Roberts and Ralph's younger brother Lou, also watch her strip naked and exercise. An angry Ralph yells at them, brandishing a bayonet. Shocked at this, Lou falls over the railing to his death, for which Ralph falsely blames Sean. Later that night, Ralph confronts Sean again, threatening to cut the boy's tongue out should he reveal anything. The sheriff questions Sean, who lies due to seeing Ralph eyeing him. The next day, Sean meets with Diane, who invites him to have tea. Diane reveals that she knows about Ralph stalking her. On their way home, Sean and she see Ralph watching them. Diane invites Sean into her house for a drink. This soon escalates into a moment of passionate lovemaking while Ralph, unknown to them, watches jealously. Diane invites Sean to her boat the next day. Ralph arrives and threatens Sean with a handheld
harpoon. However, upon seeing Diane, he flees. Diane later asks Sean to dinner, after which Ralph again threatens him with the bayonet. Diane then tells Sean's parents about Ralph's threats. The next day, Sean drives Diane home and they have a
pool party together, then make love. Diane receives a phone call from her
drifter husband telling her that he is coming back, but Diane tells him she is divorcing him. As Sean gets into his van to drive home, he is held at bayonet point by Ralph and ordered to drive to the warehouse. Sean manages to get away and arms himself with a rifle, but Ralph reveals that the gun is loaded with blanks. Ralph gets him in a
chokehold, which ends up killing him. Diane arrives on the scene, where Ralph tells her that he killed Sean so he can be with her. A horrified Diane pleads tearfully with him. Ralph, overcome with anger and jealousy at Diane's love for Sean over himself, tries to strangle her. Diane manages to stab him with his own bayonet and flees crying, leaving Ralph to bleed to death. Diane finds Sean's body, breaks down and weeps. ==Cast==