In Paris, Dr. Gogol is infatuated with theater actress Yvonne Orlac as he returns to his same box seat for her every performance. Yvonne is married, however, to concert pianist Stephen Orlac. They plan to move to England. When Stephen's talented hands are crushed in a train wreck, Yvonne asks for Dr. Gogol's help by operating to save them. Although the doctor can't save Stephen's hands, he will do anything to help Yvonne. His solution is to replace the hands with those of an executed knife-throwing murderer. Gogol's obsession with Yvonne grows while Stephen discovers that his proficiency at the piano has been replaced by an uncanny accuracy with throwing things. The doctor's next move is to play on Stephen's mental distress to convince him that he is crazy, and a murderer. It is the only way he can get Yvonne.