Vidocq. The name strikes terror in the Parisian underworld of 1818. As founder and chief of a newly created plainclothes police force, Vidocq has used his mastery of disguise and surveillance to capture some of France's most notorious and elusive criminals. Now he is hot on the trail of a tantalizing mystery - the fate of the young dauphin Louis-Charles, son of Marie-Antoinette and King Louis XVI. Hector Carpentier, a medical student, lives with his widowed mother in her once-genteel home, now a boardinghouse, in Paris's Latin Quarter, helping the family make ends meet in the politically perilous days of the restoration. Three blocks away, a man has been murdered, and Hector's name has been found on a scrap of paper in the dead man's pocket: a case for the unparalleled deductive skills of Eugene Francois Vidocq, the most feared man in the Paris police. At first suspicious of Hector's role in the murder, Vidocq gradually draws him into an exhilarating - and dangerous - search that leads them to the true story of what happened to the son of the murdered royal family.