Paul Bavian, a pseudo-spiritualist, contacts Roma Courtney with the intention of gaining control of the Courtney fortune. He tells Roma that he has communicated with her deceased brother, John, and arranges a seance at which a plastoccne mask of John's face is used to represent his spirit. During the seance, Bavian makes it appear that John was murdered by Nick Hammond, Roma's guardian. Distraught by what she has seen and heard, Roma leaves.
Dr. Houston, a psychologist, believes that the spirit of a deceased criminal can enter the body of a living person and continue to commit crimes. He meets with Ruth Rogen, the "Greenwich Village love-murderess," who is about to be executed for her crimes and gives Houston permission to perform experiments on her body after her death. Ruth hopes that her spirit will seek revenge on Bavian, the man who betrayed her to the police.
When Hammond is murdered by Bavian at a second seance, Ruth's spirit enters Roma's body. Taking on Ruth's personality and behavior, Roma lures Bavian onto her yacht and attempts to strangle him. John Courtney's spirit, speaking through the ailing Dr. Houston, communicates to Grant Wilson the location of Roma and Bavian. Wilson's arrival prevents Roma from killing Bavian, who flees from the cabin. On deck, he becomes caught in the halyard and is strangled to death. Having achieved its revenge, Ruth's spirit leaves Roma, and she is reunited with Wilson.