Bruce, the son of a rich industrial boss, is admitted to a mental sanatorium after the mysterious death of his mother. Released in a cured form, he learns from Ezil, the black housemaid, that his father has married Susan, the woman who cared for his mother until her death. Bruce is convinced that Susan murdered his mother. He and his cat Samson develop increasingly violent aggression against Susan. At the height of the war of nerves between the three, Ralph, the chauffeur, is murdered. His lifeless body looks as if it had been torn by a big cat. Is Samson, the cat, the key to everything that happens?