Anna Grimaldi, an attractive widow, lives in a luxury villa amid tropical landscape on a Caribbean island. Her late husband only left her his debts, and now she is forced to turn the villa into a luxury boarding-house. Anna worries permanently about money, and is very relieved when she finally finds guests for the season. But Anna's nephew Max is causing her concern yet again. Max, a difficult young man, is unable to stand on his own two feet. His insatiable desire for a life of luxury and his compulsive gambling keep getting him into trouble with both the criminal underworld and the police. He urges his aunt to give him money, but this time Anna is insistent that he should work with her to resolve their financial problems. Her entire attention in this respect is focused on a newly-arrived guest at the hotel. The guest is Bianca Mayers, heiress to an immense fortune, who has come to the villa to recuperate from a terrible experience: Bianca witnessed the suicide of her father Dr Mayer, a famous physician. Suffering from severe shock, she drove off in her car and had a serious accident. Since that day she has been blind. Anna offers a fraudulent business partnership to Bianca. When the latter refuses, Anna asks Max to exert his charms on Bianca instead; but Max's initial attempt to gain her affections is extremely clumsy, and Bianca rejects him decisively. The other guests at the hotel also have a keen interest in Bianca - especially Dominik, a young German businessman who has grown weary of his alcoholic and chronically jealous wife. When she notices that Dominik is pursuing Bianca she throws several violent scenes. Meanwhile Silvia Rollins, a young authoress, has made friends with Bianca - but her interest isn't selfless either. She is after some tapes containing Bianca's diary entries, and wants to use them as inspiration for her next novel. After Bianca has agreed to cooperate with Silvia, the authoress gradually begins to develop a strong erotic attraction to her. This results in a fierce argument between Silvia and her girlfriend Joan, who suddenly feels ignored. The only guest in fact who actually seems to be going out of his way to avoid the rich heiress is Dr Ruby, a married doctor, who has come to the hotel to quietly prepare a speech. The atmosphere of desire and jealousy in the villa grows increasingly intense, and finally an appalling murder is committed. One night Bianca is brutally killed with a kitchen knife. Inspector Gray, an affable man in his fifties, and his attractive young assistant Paula Anson take over the case. The fact that the murder weapon is a kitchen knife is clear proof to Gray that one of the guests or someone living in the villa must have been the murderer. The experienced policeman thus puts everyone in the villa under house arrest, for each of them had a possible motive: the widow, greedy for money, and her dubious nephew; the rejected Dominik and his jealous wife; the famous authoress and her obsessive girlfriend. Even Dr Ruby's complete avoidance of Bianca is suspect. During his visits to the villa Gray, a master of deduction, has detailed discussions with all those involved. He soon realises that the guests are playing an unpleasant game: each is trying to shift the blame on to the others. They are all anxious, and want to leave the villa as quickly as possible. Three days later the murderer strikes again - the victim this time is Silvia's secretary Joan, who is shot at during the night. As if by a miracle, she is unharmed. The guests now blame Gray for exposing them all to deadly danger by keeping them at the villa, and Dominik makes it clear to the inspector that his wife Julia is on the verge of a nervous breakdown. The following night Gray's assistant Paula notices Max stealing out of the villa to pursue his nefarious business dealings, despite the curfew imposed by the police inspector. She follows him and ends up in real danger when Max's accomplices kidnap her and threaten to kill her. Max goes back to the villa. Meanwhile, Paula manages to escape from the gangsters, and she tells Gray about what happened. The inspector decides to do nothing about Max for the time being, though, hoping that he'll give them an important lead. The inspector's hunch seems to be correct when Max inadvertently leads them to Manolo, who is hiding in the attic at the villa. Manolo is the son of one of the maids, and Max had talked him into robbing a bank. After the robbery went wrong, Manolo insisted that Max should hide him in the villa. Manolo is carrying a gun, and taking Julia as a hostage, he barricades himself in. In this situation Julia's husband Dominik shows real strength of character. He liberates Julia and succeeds in overpowering Manolo. This incident has a positive outcome: Julia discovers a new meaning in her marriage, and decides to give up alcohol for good. Everyone is convinced that it was Manolo who killed Bianca. But Inspector Gray is still unconvinced: why should Manolo have used a kitchen knife when he had a gun all the time? Gray has nothing to go on, though. One night he suddenly hears Bianca's voice: he realises that someone has placed the cassette with Bianca's diary entries into the stereo unit. Gray calls all the guests together and plays the tape to its conclusion. From Bianca's observations it becomes clear that Dr Ruby must have been her murderer. Although the whole solution seems just a bit too simple to Gray, he still has the doctor placed under arrest. Doubt continues to nag at Gray. While the relieved guests are all preparing for departure he keeps wondering who could have placed the cassette in the stereo. Listening to it again, he suddenly has an answer: the recording isn't Bianca's diary at all, but a fictitious storyline that Bianca had worked out with Silvia for her new novel! At this point Paula discovers a new clue, proving that only Joan could have known where the cassette was that Silvia had been searching for all the time. Silvia intervenes without success, pointing out that Gray has already arrested Ruby as the murderer. But when Gray proves to Joan that she faked the attempt on her life, she breaks down. She admits that she killed Bianca in a fit of jealousy, because she felt she was intruding on her relationship with Silvia.