Pocho Martin's body is found dead on the shore of a fishing village. According to the forensic Ramiro, Pocho has been assassinated, which alerts the Commissioner Carlos. Young Silvia, Pocho's friend, receives the sad news but is more concerned about her impending wedding with Andy. Crackpot Oscar speaks to Carlos of the dangerous sirens of Deer Island, evil women who attract sailors and annihilate them. When Ramiro and Carlos go to the island, they find the sisters Lila and Mary, who run a tavern / brothel near the beach. Carlos and Lila are old acquaintances and celebrate the reunion, but the murder of Pocho remains unsolved.
| Writing | Jesús Franco | Writer |
| Writing | Jesús Franco | Screenplay |
| Production | Jesús Franco | Producer |
| Production | Antonio Mayans | Production Manager |
| Costume & Make-Up | Juana de la Morena | Makeup Artist |
| Directing | Lina Romay | Assistant Director |
| Art | Carlos Spitzer | Art Direction |
| Writing | Jesús Franco | Story |
| Editing | Lina Romay | Assistant Editor |
| Sound | Julián Sacristán | Music |
| Directing | Jesús Franco | Director |
| Camera | Juan Soler | Director of Photography |