In 1944, a small Illinois town found itself at the center of one of the strangest mysteries in American history.

This week we investigate the story of the Mad Gasser of Mattoon. A mysterious figure allegedly prowling through the night, leaving victims reporting strange odors, paralysis, nausea, and fear.

As reports spread across town, panic quickly followed. Residents locked their doors, armed themselves, and searched for an attacker that nobody could seem to catch.

Was there really a phantom gasser stalking the streets of Mattoon? Or was the town experiencing one of America's earliest and most famous cases of mass hysteria?

We get into the reports, the investigation, the suspects, and the theories that surround the case.

Sometimes the most unsettling mysteries aren't about what happened...

They're about what p ...