On August 24, 1911, all French newspapers came out with sensational news: Leonardo da Vinci's painting "Mona Lisa" was stolen from the Louvre. Police Prefect Marc Lepine takes the case under personal control and entrusts the search for the national treasure of France to the best Parisian detective, Inspector Francois Drioux. During the investigation, it turns out that museum values are almost not protected. Moreover, a thorough inventory showed that in recent years hundreds of exhibits have been stolen from the halls of the museum... The director of the Louvre is in a panic, and Lepin and Driou are at a loss. How to find a robber if it could be anyone?