While vacationing in Puerto Rico, Harold and Evelyn Gern (Anthony Carbone and Betsy Jones-Moreland) go skin-diving with their friend and attorney Martin Joyce (Robert Towne). When they surface from their underwater adventure, the trio discover themselves as the only people left alive on the island. They conclude that an interruption of oxygen in the atmosphere had killed those on the surface leaving them quite alone. Now faced with the possibility of being the last people alive on the planet, the two men turn on each other in order to vie for the attention of Evelyn.