On the outskirts of Paris, two men have been found with their throats cut, and despite the common assumption that the crime is a drug-related incident, Commissaire Adamsberg becomes convinced that the deaths are the work of a serial killer with split personalities and enlists the assistance of pathologist Ariane Lagarde to help him unravel the truth.

Paris, 1761. Brilliant young Parisian police commissioner Nicolas Le Floch works under the Royal Lieutenant General of Police. Louis XV's kingdom is plagued by conspiracies and murders. With the help of his faithful assistant Bourdeau, Nicolas solves mysterious disappearances and sorts out awkward scandals. From seedy taverns to the hallways of Versailles, from brothels to prisons, he tracks and stakes out suspects, questions witnesses, gathers evidence,...