Earthmen from the future sets one half of the JLA against the other.
An impenetrable barrier surrounds the conference room of the Justice League of America. Despite their best efforts, neither Wonder Woman, J'onn J'onzz, the Manhunter from Mars, or the Green Arrow can break through the barrier. Trapped within the conference room are the Batman, the Flash, the Green Lantern, the Hawkman, and Superman. The five heroes are transported into the future, where their actions are observed by a strange, alien being. Robot arms emerge from the walls, placing the Flash & the Green Lantern inside giant test tubes. Superman attacks the robot arms, as they grasp at the Batman. Meanwhile, the Hawkman attacks the monitor screen. Above their heads, golden rods pulsate with blinding light.
Superman crashes into the test tubes holding the Flash and the Green Lantern, freeing them. While the Hawkman continues to batter away at the monitor screen, the other four heroes try to break out of the laboratory. Failing to do so, they switch tactics. The Green Lantern catapults Superman into the monitor screen, shattering it. The "alien" appears before them. In truth, he is a human being, from the year 25, 673. Thanks to the efforts of the Justice League of America, the power of the Alien-Ator has been overcome. In their far advanced age, the secrets of space had been conquered. Humanity looked next to solving the mysteries of time. Their experiments in the time stream released an unfathomable creature, one they dubbed the "Alien-Ator".
In order to enslave humanity, the creature transformed the entire populace into alien beings. Consulting their highly advanced computers, Earth scientists determined that a specific type of radiation would return them to normalcy. The radiation, though, could only be generated by the kinetic energy released by super-human beings. To this end, the members of the Justice League of America were brought to the future, and forced to exert their super-powers, until the weapon to defeat the Alien-Ator could be fully charged. However, though the Alien-Ator has been driven out of the future, it has traveled back in time to menace the present. The Justice League of America take the weapon back to their era, to combat the Alien-Ator in the 20th Century.
En route, they are attacked by a massive gelatinous monstrosity. Despite their best efforts, none of the Justice League of America are able to damage the creature, which just oozes around their attacks. Locked in a moment of time, the team realizes that they are doomed to fight the creature for eternity. The Green Lantern uses stored chronal energy to age himself to an old man. By creating this one change in the moment they're locked in, the creature ceases to exist. The Justice League of America returns to their conference room. The Alien-Ator has already transformed their teammates into aliens, and enslaved them. While the Batman repairs the weapon, damaged during the battle against the gelatinous creature, his teammates engage their former comrades in combat.
The Alien-Ator's transmutation of their teammates has made them more formidable than ever. Wonder Woman is now the equal of Superman in power. J'onn J'onzz, the Manhunter From Mars is no longer vulnerable to fire. The Green Arrow is impervious to Superman's blows. The battle rages for several moments, all the while charging the weapon with the kinetic energies being released. Though the Justice League of America falls to their altered teammates, the weapon discharges, returning them all to normalcy, and driving the Alien-Ator from their era. The Justice League of America keep the weapon firing constantly, into the time stream, to neutralize the the power of the Alien-Ator forever.