The atomic bombs dropped on Hiroshima and Nagasaki in August of 1945 unleashed a force as mysterious as it was deadly--radioactivity. In 1946, the United States government created the Atomic Bomb Casualty Commission (ABCC) to serve as a permanent agency in Japan with the official mission of studying the medical effects of radiation on the survivors. The next ten years saw the ABCC's most intensive research on the genetic effects of radiation, and...