This is one of the darkest chapters in human history—the secret atrocities committed by Japan’s Unit 731 during World War II. Hidden behind the frontlines, the unit conducted horrific biological experiments on civilians and unarmed soldiers. In this episode, we meet a collector who has spent years uncovering relics from Unit 731, and a descendant of biological warfare victims, as they shed light on a haunting, yet lesser-known, chapter of history.