Dr. Marcel Petiot ran a Paris practice with a reputation for shady dealings long before the Germans occupied France. When the occupation created a desperate population of Jews and resistance members seeking any way out of the city, Petiot offered one: a fake escape network promising passage to safety, for a price. Victims arrived at his townhouse on Rue Le Sueur and never left. This film follows the wartime investigation that eventually caught up with him, from the discovery of human remains in his property's furnace to the trial that tried to establish how many people he killed and why. Historians and archival photographs reconstruct occupied Paris as the setting that let Petiot operate for years, a city where disappearances could be blamed on the Gestapo and neighbors learned not to ask questions. The film treats Petiot's exact victim count, and his own shifting explanations for the killings, as still unresolved rather than settling on a tidy number.