The Legion has returned from the 41st century with Kel-El, a genetically enhanced Superman clone. But Imperiex, the destroyer of galaxies, has reached the 31st century first—and unleashed all of the Legion's greatest enemies. When the other Legionnaires (Dream Girl, Shrinking Violet, Sun Boy, Blok, etc.) went to the Prison Planet to stop them, they each got defeated one by one and got locked into the prison cells themselves. To restore order and combat this near-invincible foe, the Legion will once again turn to the past for help in the form of an older, more mature Superman with far greater grasp of his powers.