Christmas 1904. Under political and media pressure, the prefect is forced to organize a raid. He entrusts the dirty work to the moral police. An unidentified dead man is discovered in the Bois de Boulogne. Suicide... or murder? This investigation takes inspector Antoine Jouin into a clandestine and secret territory, where the whole of Paris comes to satisfy its impulses. Jouin will have to leave the beaten path... at his own risk, to enter a whirlwind of vice, corruption and blackmail.