Ominous dreams of Metropolis' destruction lead Superman to face off against a foe who can make his dreams come to life in "Days of Future Past."
Superman wanders the ruins of Metropolis, with no recollection of what happened or how he came to be there. A small band of armored knights approach. Upon realizing that they have encountered Superman, they begin badgering him for not preventing the atomic war. Ghostly survivors join their voices to the knights, tormenting Superman with their plaintive cries. Then, Superman wakes up. Superman assumes his guise as newsman Clark Kent and reports to work. Kent leads the day's stories with a report on a computer glitch at the Pentagon, that nearly triggered a nuclear war between the world powers. Unable to shake the feeling that this event is somehow tied to his dreams, Kent, as Superman, journeys to his Fortress of Solitude, to investigate the matter further. Superman discovers that computer breakdowns have been occurring in both the United States and the Soviet Union. Worse, the computers in the Fortress of Solitude also seem to be affected. Superman links his own mind to his computer to run a diagnostic. Sudden electrical feedback renders the Man of Steel unconscious. When he awakes, he finds himself in the town of Durvale, greeted by the Atomic Knights, a group of heroes in medieval armor, dedicated to rebuilding the world in the aftermath of a nuclear holocaust. With the Atomic Knights is the Greek God, Hercules. Superman is uncertain if he is dreaming once more, or if he's actually been transported into the future.
Word reaches the Atomic Knights that a radioactive creature is menacing the primitive population, in the ruins of New York. Superman engages the creature first, immediately getting cut down by a beam of Kryptonite radiation, spewed forth from the creature's maw. The Atomic Knights circle the creature, distracting it long enough for Hercules to smite it with one mighty blow. The whole affair has been too much for the Man of Steel. Superman questions Gardner Grayle, the leader of the Atomic Knights, on the inconsistencies of this post-apocalyptic world. The war was supposedly totally destructive, yet the Atomic Knights have plenty of goods and equipment to rebuild. Radiation poisoning would ravage mankind for years after the war, yet Durvale has no hospital. The only outward effects of the radiation, at all, manifest in the giant dogs the Atomic Knights ride as steeds, the devolved populace of New York, and impossibly fantastic creatures that breath Kryptonite. All of which Superman finds to be a bit too implausible. Furious at Superman's observations, Grayle literally throws Superman out of the world. The Man of Steel awakens, on the floor, in his Fortress of Solitude. Having recognized one of the Atomic Knights as Marene Herald, a S.T.A.R. Labs psychologist, Superman pays Herald a visit. Herald denies any knowledge of Grayle, or the Atomic Knights, but Superman spies a case file on Grayle, in her office. Using hypnosis, Superman removes a mental block in Herald's conscious memory.
Grayle had been part of an experiment to see how the average soldier would react to a post-nuclear war situation. Herald fears the experiment may have never ended. Herald leads Superman to a top secret military installation., abandoned by all appearances. Herald places her key card in the door, triggering a massive explosion. Only the Man of Steel's super-speed keeps Herald from harm. Superman tears the door from it's housing, gaining entry into the facility. There, they find Grayle, submerged in a sensory deprivation tank, still wired in to the computer simulation. Traumatized by the ghastly reality of a nuclear holocaust, Grayle's mind has somehow taken control of the simulation, re-imagining the nuclear war as merely the catalyst to a fantastic new world fraught with adventure. A world in which Grayle is recast as hero, not helpless victim. Subconsciously, Grayle's mind has begun to reach out, insinuating itself into other computer systems. Intent on turning his post-apocalyptic fantasy into reality, it is Grayle who has been responsible for pushing the world to the brink of nuclear war. Some part of Grayle's mind was aware of his actions in the real world, thus he reached out to Superman to stop him. Now, though, Grayle has completely rejected the Man of Steel, giving himself completely over to the computer simulation.
Superman moves to disconnect Grayle from the computer simulation. Suddenly, he is attacked by an enormous robot, clad in the medieval armor of the Atomic Knights. Originally intended to be piloted by soldiers in the aftermath of a nuclear war, Grayle's mind commandeers the true Atomic Knights, and turns them on Superman. Superman is taken aback by the strength and resiliency of the robot knights. Herald moves to disconnect Grayle from the computer simulation, but is scooped up in the metal gauntleted fist of an Atomic Knight. Superman informs Grayle that, to maintain his fantasy world, Grayle's fellow Atomic Knight is about to murder Herald, the woman Grayle loves. The Atomic Knight with Grayle's personality attacks the Atomic Knight holding Herald. The two Atomic Knights begin fighting over Herald. Though both are controlled by Grayle's mind, only one speaks with his voice. The other is, ostensibly, Douglas Herald, Marene's brother. Herald's revelation that Douglas is not truly her brother, but, in actuality, her husband, shatters the foundation of lies Grayle's built his world upon. Unfortunately, it may have come too late. Grayle's subconscious mind initiates a nuclear launch sequence. Superman, operating at super-speed, reprograms the entire computer system, stopping the countdown with one second to spare. Superman severs Grayle's links to the world's computers, and finally releases him from the computer simulation. Grayle is overwhelmed by the guilt of his actions. His time in the simulation, though, has given him a new outlook on the Cold War. Grayle posits that mankind shouldn't be trying to determine how to survive a nuclear war, but, instead, should be focused on how to keep one from ever occurring.