Fantomas having just escaped into the sewers of Paris, Juve and Fandor find themselves with few clues to go on until the great detective is approached by a Committee of Insurance Companies against Theft with a mission–to protect a secret document which details the precise location of the jewels of Empress Eugenie, wife of Napoleon III. Knowing Fantomas will try to steal this priceless treasure map, Juve sets a trap for the Arch-Criminal in the pleasure resorts of the Parisian suburbs in this, the thirty-fourth book of the series.