Superman has turned himself in to the authorities - and now, it's up to Batman, Wonder Woman, Steel and Krypto to plunge into the Phantom Zone and discover Doomsday's origins. But something has happened to this endless void - Mongul, the despot leader of Warworld, and the Kryptonian Non are out to kill anyone else that trespasses their area. Within the deepest part of the Phantom Zone lurks someone else who will either help the team or doom them!