Nine people sail a yacht to a deserted rocky island for a holiday in old Uberto's villa. The host is accompanied by a group of family members. The men's only thought seems to be having sex with anyone else's wife. One by one, the guests are killed by an unidentified assailant; Elisabetta, half-mad, claims it's the ghost of Charlie, her lover, who had been killed twenty years before by Uberto and his two sons. The survivors cannot leave the island ( the yacht has disappeared) and are easy prey for the murderer. Vincenzo, now the only one left, discovers the truth...