The marvelously theatrical George Zucco plays a dual role as the dysfunctional Clayton twins who also happen to be doctors. Predictably one twin is good, and the other evil. Dr. Lloyd Clayton is forced to kill his brother Elwyn in self-defense. Elwyn, who happens to be well versed in the dark arts, returns from the grave to exact his revenge. Lloyd viciously slays Elwyn's colleagues, leaving a mounting trail of evidence that point to the surviving sibling. Lloyd is aided in his evil acts by a hunchbacked assistant played by Dwight Frye.