The Podcast details the investigation into Dr. Marcel Petiot, a French physician and psychopath who used the chaos of Nazi-occupied Paris to commit a series of murders. Petiot posed as a resistance member running an escape network, luring victims with promises of safe passage to South America, then killing and disposing of them. The investigation, led by Commissaire George Masu, uncovered a gruesome scene at Petiot's home, revealing numerous victims. Petiot's trial became a sensational event, with his charismatic defense only partially obscuring the overwhelming evidence of his crimes. Ultimately, he was convicted and executed, his story a chilling blend of wartime opportunism and psychopathy.