On the eve of their honeymoon, Linda and Allen embark on a sun-kissed voyage to Acapulco, riding the waves aboard a yacht owned by Burt. They are accompanied by Burt's wife, Claire, and by another couple, Mark and his wife Isabel. The group shares a history—Burt and Mark are Vietnam War veterans who were friends with Allen—so their trip feels like a test of old loyalties and buried memories. Before the vessel even casts off, a marina worker is stabbed to death by a shadowy intruder in black pajamas, an ominous spark that hints at danger lurking below the surface.
As the yacht sets sail, wartime flashbacks pull the trio of men back to the brutal acts they committed during their tour in Vietnam, including the killing of villagers. These memories haunt their present, heightening tension aboard the boat and bringing to light unease that slips into romantic and sexual undercurrents among the couples. The atmosphere grows increasingly claustrophobic as the ship is vandalized, crippling some navigation and communications equipment and leaving the crew stranded with their fears. Amid the growing paranoia, Isabel begins to act erratically, repeatedly insisting that “the moon is in Scorpio” whenever misfortune strikes, a superstition that others start to fear as a message rather than a sign.
Tragedy quickly follows: [Mark], [Burt], and [Claire] are gruesomely killed, leaving [Linda], [Allen], and [Isabel] as the survivors. The tension shifts to a deadly dynamic among the remaining passengers, and the suspense tightens as fear and guilt drive decisions under the hot sun and the creaking hull. The danger culminates when [Allen] is killed, and Linda searches the yacht to find Isabel armed with a peculiar grappling hook—the murder weapon that will seal the fate of the remaining passengers.
A violent confrontation ensues between Linda and Isabel, and Linda ultimately overpowers her, stabbing Isabel to death with the grappling hook. The entire sequence of events is revealed to the audience through flashbacks from Linda’s perspective, making her the sole survivor whose memories carry the weight of the entire voyage. The film opens with a teaser: an unseen person escaping from a mental institution, while Linda lies in a hospital bed under the care of a doctor. The narrative closes with Linda being released from the hospital after she has recounted her story to the police, leaving the audience with a chilling sense of what really happened on that doomed cruise and what it implies about the truth she has chosen to tell.
