Ten strangers are lured to an island mansion on an isolated rock near the Devon coast. Cut off from the mainland, with their generous hosts mysteriously absent, they are each accused of a terrible crime. When one of the party dies suddenly, the guests realise they may be harbouring a murderer among their number. The ten strangers include a reckless playboy, a troubled doctor, a formidable judge, an uncouth detective, an unscrupulous mercenary, a religious spinster, two restless housekeepers, a highly decorated general and an anxious secretary. As one by one they are picked off, the dwindling group must stay one step ahead of their deadly stalker. Who will survive? And who is the killer?