Bored with her routine life in London, 25-year-old Lucy Irvine (Amanda Donohoe) answers a newspaper classified ad placed by 49-year-old Gerald Kingsland (Oliver Reed), who seeks a female companion to spend a year isolated on a deserted South Pacific island. To satisfy immigration laws requiring cohabiting couples to be married, they undergo a marriage of convenience in Tuvalu before being dropped off on Tuvalu's uninhabited island of Tuin. Once isolated, serious ideological and physical clashes emerge: Gerald envisions a traditional, sexually active domestic marriage, whereas Lucy views the expedition strictly as a survival challenge and refuses his sexual advances. As physical deprivation, lack of fresh water, and tropical illness take hold, their paper marriage collapses into a desperate struggle for survival and psychological endurance.