Mount Omine in central Japan has long been considered the spiritual heartland of the ascetic tradition known as Shugendo. Japan-based American journalist David Caprara lives at the foot of the mountain. One day he comes across a rusty airplane engine in a local museum. It once powered a US heavy bomber B-29 Superfortress which was used in air bombings during World War II. Intrigued, Caprara begins a quest to track down the story behind the engine. With the help of experts in Japan and the US, he obtains key wartime documents that confirm the B-29 had crashed after a bombing raid on Osaka on June 1, 1945 and that 4 airmen survived only to become prisoners of war. He also meets elderly people who witnessed the events. Caprara eventually pieces together the fate of the American fliers and the stories of those whose lives crossed theirs on the revered mountain.