Opening in the rundown city of Hiroshima, we witness the events leading up to the bombing through the eyes of Gen, a young boy growing up in the post-war Japan. Fortunately when the bomb detonates, Gen is shielded by a stone wall. As he runs home, he sees victims of the bomb blast staggering around shocked and helpless in the rubble. When Gen reaches home he finds that his house has collapsed, trapping his father, brother and sister in the wreckage. What follows is a night-marish journey into the unimaginable horrors of atomic war.