Overview: On March 11, 1944, the nauseating smoke that escaped from the chimney of the mansion at 21 rue Le Sueur, in Paris, led the neighbors to alert the police. The owner, a certain Doctor Petiot, is absent. The firefighters break a window to enter. In the cellar, near the boiler which is running at full speed, they discover human remains. It quickly turns out that Doctor Petiot murdered those he claimed to want to help leave occupied France.