Frank Clamart, the abandoned, illegitimate son of a wealthy merchant, flees to Paris and joins a gang of "society crooks" led by Chu Chu and Leontine Petrovsky, his sometime lover. To prove his prowess to the gang and to Leontine, with whom he has fallen in love, Frank attempts to rob the house of a well-to-do family but is shot by the owner. As Leontine escapes unharmed, Frank is inspected by the owner's wife, who, recognizing a birthmark on Frank's wrist, identifies him as her husband's missing half brother. Nursed back to health by his sister-in-law, Frank agrees to renounce his life of crime, but when a jealous Chu Chu breaks into the house and steals the family jewels, Frank is suspected. To exonerate himself, Frank tricks Chu Chu and retrieves the gems. Determined to have revenge, Chu Chu tries once more to rob the house and, when caught by Frank, shoots him in the shoulder.