Synopsis

Actress Yvonne Orlac (Frances Drake) rests after her final performance at the 'Théâtre des Horreurs' (styled after the Grand Guignol) in Paris, France. As she listens to her husband Stephen Orlac (Colin Clive) play the piano on the radio, she is greeted by Dr. Gogol (Peter Lorre), who has seen every show featuring Yvonne, and unaware of her marriage, is aghast to learn that she is moving to England with her husband. Gogol leaves the theater heartbroken, buys the wax figure of Yvonne's character, refers to it as Galatea (from the Greek myth), and arranges that it be delivered to his home the following day.

Stephen Orlac is on a train journey from Fontainebleau to Paris, where he sees murderer Rollo the Knife thrower (Edward Brophy), who is on the way to his execution by guillotine. (Gogol later witnesses the execution, along with the American reporter Reagan (Ted Healy)). Orlac's train crashes later that night, and Yvonne finds her husband with mutilated hands. She takes Stephen to Gogol in an attempt to reconstruct his hands, and Gogol agrees to do so. Gogol uses Rollo's hands for the transplant, and the operation is a success.

The Orlac couple are forced to sell many of their possessions to pay for the surgery, while Stephen finds he is unable to play the piano with his new hands. When a creditor comes to claim the Orlacs' piano, Stephen throws a fountain pen that barely misses his head. Stephen seeks help from his stepfather, Henry Orlac (Ian Wolfe). Henry denies the request, upset that Stephen did not follow in his line of business as a jeweler. A knife thrown in anger by Stephen misses Henry, but breaks the shop front's window. Gogol meanwhile asks Yvonne for her love, but she refuses. Stephen goes to Gogol's home and demands to know about his hands, and why they throw knives. Gogol suggests that Stephen's problem comes from childhood trauma, but later confirms to his assistant Dr. Wong (Keye Luke) that Stephen's hands had been Rollo's.

Gogol then suggests to Yvonne that she get away from Stephen, as the shock has affected his mind and she may be in danger. She angrily rejects Gogol, whose obsession grows. Henry Orlac is murdered, and Stephen receives a note that promises that he will learn the truth about his hands if he goes to a specific address that night. There, a man with metallic hands and dark glasses claims to be Rollo, brought back to life by Gogol. Rollo explains that Stephen's hands were his, and that Stephen used them to murder Henry. He also claims that Gogol transplanted his (Rollo's) head on to a new body...flashing a leather-and-metal neck brace as "proof!"

Stephen returns to Yvonne and explains that his hands are those of Rollo, and that he must turn himself in to the police. A panic-stricken Yvonne goes to Gogol's home, and finds him completely mad (after he has come home and shed his elaborate disguise). Gogol assumes that his statue has come to life, embraces her, and begins to strangle her. Reagan, Stephen and the police arrive, but are only able to open the observation window. Stephen produces a knife and throws it at Gogol, then finds his way in. Gogol dies as Stephen and Yvonne embrace.