Frank Clamart, 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. Frank pursues Chu-Chu in a taxicab, forces him over a cliff, then leaves with his new love, the cab driver, who fires a shot that kills Chu-Chu.