France, 1871. The Parisian revolutionaries have risen up against the French government and have taken control of the streets of Paris: it is the Commune. The government's army lays siege to the city to cut off the Commune. The battle is bloody. Under these chaotic circumstances, some partially flayed bodies appear, completely drained of blood. The leaders of the Commune give responsibility for the investigation of the case and capture of the killer to a woman. That woman is Sophie Blanchet, who studies the behaviour of murderers alongside her job working in a psychiatric hospital. The Commune put two men at her disposal: Fabian, a young revolutionary, and Leo, who works for the Commune after spending ten years as a prisoner on a Polynesian island. Together they will have to face twin dangers: the army's bloody suppression of the revolt and the killer himself. The 'City of Light' is cloaked in bloody darkness.