The housekeeper Lucille lives in an old castle with her nephew Colin and Falaise, the daughter of the landlord, André. All the guests of the villa are systematically killed by the three of them, then they are saponified in the dungeons of the castle. Falaise is convinced that she killed her father, who died several years earlier. The arrival at the castle of a man who pretends to be Andrè who made a facial plastic (but in reality he is a police inspector) will solve the mystery: Falaise, in reality, is none other than Lucille’s daughter, Esther. Lucille, with the complicity of the two boys, killed all those who approached the house in order to cover a series of events that occurred thirteen years before. A gang of criminals had tried to kill Mr. Gardère, who had managed to escape. Lucille had faked him death at sea, remaining the sole owner of the castle. On that terrible night the killer had raped Falaise who, believing him to be the father. But in reality things had gone differently. Esther and Falaise were shocked: the first, convinced she was her friend, had begun to kill all the men who remind her of her father, while the second had been interned in a clinic. Colin, also suffering from serious mental disorders, had been easily duped by Aunt Lucille, who was actually the real instigator of the murder of Mr. Gardère, as well as a lover of the killer. It was she who killed him, getting rid of the two men and the memory of the three boys in one fell swoop. Eventually Falaise will resume possession of his castle. Esther and Colin will be arrested. Lucille, now discovered, will commit suicide by inhaling cyanide fumes dissolved in warm water.