When Parisian actress Yvonne Orlac (Frances Drake) announces that she is leaving the stage to be a full-time wife to her concert pianist husband, Stephen (Colin Clive), brilliant surgeon Dr. Gogol (Peter Lorre), who is obsessed with Yvonne, is crushed. So when Stephen loses his hands in a train wreck, Gogol agrees to Yvonne's request to graft another pair of hands onto Stephen. But before long, Stephen realizes that his hands seem to have a mind of their own. He can no longer play the piano -- but he can throw knives with deadly accuracy! It turns out the hands belonged to an executed murderer, and they never lost the desire to kill. As Stephen slowly goes insane, Gogol professes his love for Yvonne, but she rejects him. Gogol vows to hasten Stephen's demise to drive Yvonne into his own arms.