The story involves a kindly small-town physician Doctor Lloyd Clayton (Zucco), who has secretly murdered his twin brother Elwyn, because of Elwyn's deep involvement in satanism occult practices. Only Elwyn's hunchback assistant Zolarr (Frye) suspects the good doctor of doing away with his master and confronts him on this matter, but the doctor maintains that he only acted in self-defense when his brother had become a danger to society.