In September of 1944, residents of Mattoon, Illinois began reporting a prowler outside their windows — one who left no footprints, no face, and no trace. Only a smell. A sweet, sickening gas that paralyzed legs, caused vomiting, and sent families to the hospital. The local newspaper ran the story. Then more victims came forward. Then more. The town was terrified, the police were baffled, and the attacker was never caught — because some investigators came to believe there was never an attacker at all.

Host Shawn Spainhour takes you into the anxious world of wartime small-town America — a community stretched thin by rationing, absent husbands, and factory fumes — and walks you through one of the most debated cases of mass psychogenic illness in modern history. Was the Mad Gasser real? A chemical leak? A copycat? Or something that spread not t ...