Geoffrey, a young and impoverished writer, is desperately in love with Mavis, who lives at his boardinghouse and is also pursuing a writing career. Unable to marry her because of his poverty, in his anger he curses God for abandoning him. Soon Geoffrey meets Prince Lucio de Rimanez, a wealthy, urbane gentleman who informs Geoffrey that he has inherited a fortune, but that he must place himself in the Prince's hands in order to enjoy the fruits of his inheritance. What Geoffrey doesn't know is that Prince Lucio is actually Satan, who is using Geoffrey as an experiment to show God that he can corrupt anybody.

After completing a novel in his London garret, Geoffrey Tempest meets Mavis Claire, another struggling writer, and they drink to the success of his novel, in which he rails at God and fate. When his publisher rejects his supernatural theme, Tempest meets Rimanez, a mysterious nobleman, who takes him to a sumptuous hotel, where he is transfixed by the lovely Princess Olga. Informing Geoffrey that he has been made heir to a fortune, Rimanez arranges for his marriage to Olga; and following a successful courtship, there is a spectacular wedding. Married life, however, proves a failure for Geoffrey, and while dining with wealthy friends he sees Mavis, forlorn and poorly clad; when he rises to follow, Rimanez reveals his identity as Satan and threatens to strip him of his riches. Morning finds Geoffrey in his garret, reconciled with Mavis.