King Louis XIII sends Chatellerault to win Roxalanne de Lavedan, hoping to keep the girl's fortune within the kingdom. When Chatellerault reports that Roxalanne is unapproachable, Bardelys, a courtier, wagers his entire estate against Chatellerault's that he will capture the girl within three months. En route, Bardelys finds a dying man and is given a miniature and some letters bearing the name Lesperon, whose identity he assumes. Finding that Lesperon is a traitor, he seeks shelter in the Lavedan estate, and though she is frightened, Roxalanne allows him to court her. Another suitor, St. Eustache, warns her that Lesperon is engaged to Mademoiselle Mersac. Bardelys is arrested for treason, but the arrival of the king saves him from execution. Roxalanne marries Chatellerault to save Bardelys' life, but Chatellerault is killed in a duel with the courtier, who is thereafter joined with his beloved.