This collection of detective short stories follows the enigmatic Jim Barnett, who operates the Barnett Agency in pre-war Paris. He works entirely alone, offering his services for free while utilizing levies and poetic justice rather than traditional police fees. Inspector Béchoux, a dandy of the Paris police force, frequently encounters Barnett and gradually suspects that the brilliant private detective is actually the legendary King of Crooks, Arsène Lupin in disguise.
The narrative unfolds through several intricate cases, beginning with the investigation of Baronne Assermann. Her diamond and pearl necklace is stolen and replaced with imitation pearls through a clever trick involving her ailing husband and a plumbing system. Barnett solves the mystery with characteristic arrogance, uncovering domestic bitterness and hidden revenge.
Another case involves the murder of a miserly bookseller, Vaucherel, where a forged canvas alibi and an intricate plot surrounding a royal love letter belonging to King George the Fourth are masterfully exposed by Barnett's razor-sharp intellect.
In subsequent adventures, Barnett investigates a tragic baccarat game in Rouen resulting in murder, uncovers the theft of church treasures through an ingenious optical illusion involving gold teeth, and tracks down stolen African mining shares hidden inside a politician's portfolio.
The volume culminates in a tense struggle where Béchoux finally attempts to unmask Barnett as Arsène Lupin during a high-stakes political scandal involving a missing photograph and a tragic abduction, cementing the eternal cat-and-mouse game between the master thief and the law.
