A wild bank robbery using an alien ray gun alerts Clark Kent to something strange and unearthly. The deadly ray even hurts Superman. The US President disappears, and Superman learns of a huge asteroid in nearby space, apparently under human control. Flying to the "secret planet," he learns that a piece of his home world survived, a city called Kryptonia. He also finds himself without super powers, neutralized by the Kryptonite which is the asteroid itself. The colony is ruled by a cruel tyrant named Zonar, with plans to colonize and enslave the Earth. With the help of his young cousin Kara and an aged scientist, Superman returns to Earth to warn humanity. Zonar's legion of unmanned drone saucers destroys landmarks and people, and he gives Earth an ultimatum. As Clark Kent, Superman bids goodbye to Lois Lane, and does so again at Cape Canaveral as Superman, boarding an unstable atomic rocket to return to Kryptonia. Lois and Jimmy Olson sneak aboard, much to Superman's disapproval. With the odds against him, Superman returns to the remnant of his home world for a final face-off.