Lupin is a brave and outspoken fourteen-year-old boy, a paragon of honor. He enjoys a notorious reputation among Parisian criminals and lives in the infamous La Forka building, surrounded by forgers, bank robbers, and burglars. But for him, theft is a matter of honor; he has clear goals and always shares his loot with orphans. One day, Cyrano, the elephant trainer, and Clarisse, the graceful acrobat from the Defère Circus, visit him. Cyrano's brother, a mechanic, has disappeared, and the police are trying to cover it up. When Lupin deduces that Monsieur Charp is behind the kidnapping, he sets out to solve the mystery. He can't back down; he, too, has an old score to settle with Monsieur Charp. The heroes join forces to achieve their goal and thwart Monsieur Charp's string of crimes, resorting to disguises and tricks.