Michel (Martin LaSalle) goes to a horse race and steals some money from a spectator. He leaves the racetrack confident that he was not caught when he is suddenly arrested. The inspector (Jean Pélégri) releases Michel because the evidence is not strong enough. Michel soon falls in with a small group of professional pickpockets who teach him their trade and invite him to join them on highly coordinated pickpocketing sprees in crowded public areas.
Visiting his mother, Michel meets Jeanne (Marika Green) who begs him to visit his mother more often. His friend Jacques goes on a date with Jeanne and invites Michel along. But after stealing a watch, Michel leaves Jacques and Jeanne at the carnival. While they are at a bar, the inspector asks Michel to show him a book by George Barrington about pickpocketing, bringing the book to the police station on an appointed date. Michel goes down to the station on that day, with the book. At the station, the inspector barely glances at the book. Michel returns to his apartment realizing that it was all just a ruse to search his apartment. However, the cops failed to find his stash of money.
Michel’s mother dies, and he goes to the funeral with Jeanne. Later, the inspector visits Michel in his apartment, and tells him that his mother had some money stolen, but later dropped the charges, probably knowing the thief was her son. The inspector leaves without arresting Michel, who decides to leave the country. He travels from Milan to Rome and ends up in England where he “spent two years in London pulling off good jobs”, but throws his earnings away on alcohol and women.
Returning to France, Michel returns to Jeanne, who has had a child by Jacques but did not want to marry him and is now left with nothing. Michel begins to work again to support her, but gives into temptation and goes back to steal at the horse track, where he is caught by a plainclothes policeman. Jeanne regularly visits him in jail. On one such visit, Michel realizes he is in love with her.