Overview: Two years after it began, Japan's surprise attack on Pearl Harbor finally draws America into the fray of World War II. As their troops mobilize, the nation is gripped by the fear of another assault-this time against civilians on their own home soil. But did Imperial Japan really have a weapon that could turn their nightmare into a reality? In their hunt to uncover the extent of Japan's wartime plans, historian Sam Willis and urban explorer Robert Joe dig deep into the work of a secret research unit of the Imperial Japanese Army and their dark research into the workings of a deadly weapon.