Paris, 1991. The true story of Franck Magne, a young inspector starting out in the Criminal Investigation Department at 36 quai des Orfèvres, in the Crime Squad. His first case deals with the murder of a young woman. His investigation leads him to study similar cases that he's the only one to link together. He's quickly confronted by the reality of police investigation work: the lack of equipment, bureaucracy... For 8 years, obsessed by this investigation, he'll hunt the serial killer that no one else believes exists. As a decade goes by, the victims multiply and leads become muddled. The gap between the brutal murders grows shorter. Franck Magne hunts down the monster that begins to emerge, so as to stop him for good. The inspector from the Crime Squad becomes the architect of the most complex and vast investigation ever undertaken by the French Criminal Investigation Department. During it, Magne crosses paths with Frédérique Pons, a dedicated lawyer determined to understand the destiny of the man hidden behind this merciless killer. The film plunges us into 10 years of investigation, amongst opinionated cops, determined judges, conscientious forensic policemen, and impassioned lawyers who will all be affected by this case that became the sensational "Guy Georges, the killer of Eastern Paris" case.