The title refers to the radioactive fallout which descended upon ruined city of Hiroshima after the dropping of the first atomic bomb. Young bride-to-be Yoshiko Tanaka has the misfortune to be visiting Hiroshima on the day of the explosion. Incredibly, she is unhurt; she returns to her own village, across the bay from Hiroshima. Unfortunately, her townsmen have been profoundly affected by the 'black rain'; over the next five years, the poison in their systems slowly but surely erodes their souls. In a tragic state of denial, Yoshiko's former friends insist that they can't be sick-it must be the girl who is bringing sickness to them. Now a pariah, Yoshiko's life is shattered as surely as if the bomb had disintegrated her upon impact.