In 1880, Sir Robert Cargrave, a London physician known for his experimental work in paralysis treatment, is summoned to Gorslava by the mysterious Baron Sardonicus-who is now married to Cargrave's former wife, Maude-to treat his disfigurement. When Cargrave arrives, he finds the masked baron is a cruel sadist who has threatened to harm Maude if he is not successfully cured.