18th century English aristocrat Sir Percy Blakeney leads a double life. He appears to be merely the effete aristocrat, but in reality is part of an underground effort to free French nobles from Robespierre's Reign of Terror.

Lawrence Percival Van Huyler, a society fop, protests against the necessity of living up to his snobbish family's blue-blooded traditions. His fiancée, Alicia Vanderveldt, abandons him for Richard Barnaby, who ridicules the pampered Lawrence and brags of his own daring exploits in foreign countries. While the Van Huyler estate is undergoing renovation, Lawrence uncovers a box containing a confession written by the family's founder, Peter Van Huyler. In it, the patriarch admits that he was actually an Irishman of humble birth who made his fortune engaging in piracy on the high seas. Delighted, Lawrence takes a construction job and adopts a fighting attitude, challenging those who had previously made fun of him.