Narcisse is a doorman for a jeweler but dreams of becoming a private detective. The Criminas agency hires him and he comes to the aid of his former boss's nephew, accused of stealing jewelry. He first passes for the accomplice of the young man but soon discovers the culprit.
François Vidocq has deserted to go back to his wife and kids, so he becomes a thief. Unfortunately, he finds she had become Manon-la-blonde, mistress of a rich man named Ouvrard, and his children have disappeared. He offers his services to the chief of intelligence service and begins a fight...
Maxime, heir to an old provincial family, is deeply in love with Maud whom he makes his fiancée. But learning that the young girl's life has not always been beyond reproach, he refuses to marry her and returns to his castle in the company of his sister who, happier than him, has met a man worthy...
