After being exposed to radiation, a man grows into a giant with a disfigured face and goes on a rampage in Los Angeles. The authorities try to stop him, but their efforts are hindered by bureaucratic inaction and the monster's own tragic past.

When Lt. Col. Glenn Manning is exposed to radiation during a nuclear testing accident, he begins growing in size. As he continues to grow, he becomes increasingly volatile and destructive, causing chaos in Las Vegas and other cities. Eventually, he becomes a giant towering over the city skyline, leading to a final showdown with military forces.