Mad scientist Dr. Markoff (J. Carrol Naish) becomes fascinated with Patricia (Wanda McKay), the daughter of concert pianist Anthony Lawrence (Ralph Morgan). When Lawrence presses Markoff to leave her alone, the doctor knocks him out and injects him with a secret serum that grotesquely distorts his features. Markoff offers to reverse the effects if Patricia will marry him, but Lawrence refuses the offer and confronts the doctor, whose tactics grow increasingly desperate.