Mike and Tony Petrakis are a Greek father and son team who dive for sponges off the coast of Florida. After they are robbed by crooks, Arnold and the Rhys brothers, Mike decides to take his men to the dangerous 12-mile reef to dive for more sponges. Mike suffers a fatal accident when he falls from the reef leaving Tony to carry on the business. But now he has a companion, Gwyneth Rhys.

An unlucky woman’s mother is murdered by a scarf-wielding killer named Silk, leaving the woman injured, traumatised and suffering from amnesia. She’s committed to a mental institution, where Silk follows her, looking for the papers he was trying to get from her mother. And Silk’s only the beginning of her problems, since the asylum is run by a mad doctor, performing experiments in chemical lobotomies!