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.—Pamela Short

Trouble comes early in the career of Frank Clamart, known later in life as "The Tidewater Clam." As a newborn he left alone when his mother, realizing that her child's father is not her legal husband, commits suicide. But before doing away with herself she places the infant in an orphanage. Frank spends 10 years there until, finally goaded to desperation by the brutality of the attendants, he rebels and runs away. Burglary as a fine art is his conception for the next 15 years and he becomes known as one of the most expert cracksmen in the business. To escape the police's too-close vigilance, he flees to Paris, where he meets Leontine, an adventuress; Chu-Chu, the shearer; Ivan, the "fence"; and Jeff the Red. Frank falls victim to Leontine's charms, much to Chu-Chu's disgust. Clamart's reputation has preceded him to the continent, and one night, on Chu-Chu's dare, he effects an entrance to the well-guarded estate of his foster-brother, of whose existence he has never known. He is accompanied on the expedition by Leontine, garbed in her famous gown which is known in under-world circles as causing her to "blend with the night." The "Clam" is shot down in his endeavor to rob the place, and is recognized by his brother by a means of diamond-shaped scar on his arm. His repentance follows, but his erstwhile accomplices rob the home of his benefactor, which puts him under suspicion. However, he recovers the stolen goods in short order from Chu-Chu, who had taken them. Chu-Chu continues the feud, and in another effort to rob the home of Clamart's brother, shoots the Clam in the shoulder. The latter, in his search for his assailant, several days later, jumps into a taxicab. He succeeds in running his enemy over a cliff and injuring him severely. Later, after Clamart seeks a truce, they come together again, but just as Chu-Chu is about to kill Frank, Rosalie, the driver of the cab, who is secretly in love with Clamart, kills Chu-Chu. Later, Frank and Rosalie, the former having broken away from his lawless companions, declare their love for each other.—Moving Picture World synopsis