M'sieu' La Rogue, a fencing master, conducts a salle d'arme and is raising a young nephew. A woman dies in an apartment above and her daughter, a playmate of the nephew's, is taken in by La Rogue and they grow up together. When grown, they fall in love and the girl is studying music. At the studio, the girl meets one, Marode, a roué and an expert duelist, from Paris. The nephew is a bit of a swordsman himself, being an assistant to La Rogue. Marode is attracted by the girl and seeks her favor. The nephew hears of it and knows of Marode's character. There is a quarrel, a challenge, and Marode is to meet the boy. La Rogue has been ill and is partly paralyzed. He is wheeled in his chair to witness the duel, during which the nephew is wounded. The old man, shocked into life by the sight of his boy's hurt, rises and engages Marode in the duel and kills him. The girl and the nephew then renew their love and are married.