NIGHTMARE CASTLE

Stephen Arrowsmith, a scientist, has his home laboratory in the castle owned by his wife Muriel. Stephen finds her having sex with a gardener, David. He attacks and disfigures David with a hot poker and burns Muriel's body with acid. Before electrocuting both of them, Stephen is told that he is not Muriel's heir, but that the estate has been willed to her stepsister, Jenny, who is mentally unstable. Stephen removes David's and Muriel's hearts and hides them in an urn. He uses their blood to rejuvenate his aged servant, Solange.

Sometime later, Stephen marries Jenny, planning to have the rejuvenated Solange drive her insane. Jenny begins having nightmares, which include the sound of beating hearts and Muriel's voice urging her to murder Stephen. Stephen brings Dr. Derek Joyce to the castle to treat Jenny, who becomes convinced that supernatural forces are at work. Joyce discovers the hidden hearts of Muriel and David. The murdered dead return as ghosts. Muriel burns Stephen alive while David reduces Solange to a skeleton by draining her blood. Dr. Joyce then burns the disembodied hearts and leaves the castle with Jenny.

The ghosts of Muriel and David return to kill Arrowsmith and Solange, while Dr. Joyce destroys their hearts and escapes the castle with Jenny.

The film’s climax sees supernatural vengeance fulfilled as the wronged lovers mete out poetic justice on their tormentors. Destroying the hidden hearts severs the spirits' ties to the mortal world, allowing Jenny and Dr. Joyce to break free from the castle’s cycle of cruelty and obsession. The ending underscores punishment for sadistic hubris and the ultimate triumph of the innocent over the manipulative.