 William Wilson, a corrupt young aristocrat, has always been harassed by his double. Since he was a child, this homonymous character has turned up preventing his faults and condemning his evil actions. The film starts in Rome when - after a flashback recalling the unwanted intruder, Wilson is to carry out one of his deeds: to seduce a young duchess married to his enemy. William tries to lure his hated pursuer, who eventually becomes visible at Duke di Boglia s masked ball and is arrested. In one of the deserted chambers of the palace Wilson challenges his double to engage in a sword fight.