Dr. Hohner (Karloff), theatre physician at the Vienna Royal Theatre, murders his mistress, the star soprano when his jealousy drives him to the point of mad obsession. Ten years later, another young singer (Foster) reminds Hohner of the late diva, and his old mania kicks in. Hohner wants to prevent her from singing for anyone but him, even if it means silencing her forever. The singer's fiancée (Bey) rushes to save her in the film's climax.