The film revolves around Vandal Savage's plot to exterminate the greater part of the human population and start a new civilization. To ensure that the Justice League is unable to stop him, Savage hacks into the Batcomputer and steals contingency plans devised by Batman to bring down his teammates should they ever go rogue. Savage assembles a group of supervillains with personal vendettas against the heroes and pays them richly to simultaneously attack the members of the League using lethal variations of the plans.
The villains each do their part to take out the Justice League:
- Batman is informed by Alfred Pennyworth that the bodies of Thomas and Martha Wayne have been exhumed and are missing. When Bruce Wayne arrives at his parents' graves, he is ambushed by Bane. The emotional distraction is enough to grant Bane the upper hand and render his adversary unconscious. Bruce is then placed into his father's coffin which is reburied. He wakes up to the horrifying prospect of dying of asphyxiation next to his father's corpse.
- Martian Manhunter, in his human identity of John Jones, is celebrating his birthday with his colleagues from the police force. He receives a drink from a mysterious woman, who is actually Ma'alefa'ak in disguise. The drink is laced with magnesium carbonate, which is poisonous to Martian biology. The Manhunter's body is capable of curing itself, but only by sweating out the magnesium which is highly flammable. Ma'alefa'ak uses a lighter to set his enemy on fire (the Manhunter's only weakness), leaving him to burn alive without the possibility to extinguish the flames.
- Wonder Woman is attacked by Cheetah who scratches her arm, sending nanorobots into her bloodstream. The microscopic machines attach themselves to her brainstem and begin broadcasting directly into her visual and auditory sensors. This fools Wonder Woman into thinking that everyone in her vicinity is a duplicate of Cheetah. The illusion is designed to exploit her competitive nature, by sending her into a never-ending battle. Since she would never surrender, she will force herself to fight until she suffers an epileptic seizure or a heart attack.
- The Flash is lured into a trap by Mirror Master, who pretends to be robbing a train. The villain then uses a hologram of an elderly woman to create the illusion that he had a hostage. The whole scenario is only intended to trick the Flash into placing his arm into a booby trap that attaches a bomb to his wrist. The bomb will explode and kill everyone within three miles if the hero tries to remove it or if he does nothing. The only way to prevent the explosion is to run and never decelerate.
- Green Lantern is called upon by the FBI to deal with a group of terrorists who have taken hostages into a salt mine. However the truth is that both the terrorists and the hostages are sophisticated androids. The entire setting is part of a complex deception that fools Green Lantern into thinking that innocent lives are lost due to his overconfidence. The hero is also exposed to a synthesized version of the Scarecrow's fear gas that undermines his will. Finally, Star Sapphire shows up and exploits his fears, convincing him that he does not deserve the power he wields. Green Lantern renounces his ring, without which he cannot escape from the collapsed salt mine. The weakened hero resigns to his fate.
- Superman is lured to the roof of the Daily Planet by a disillusioned former employee, who threatens to commit suicide by either jumping off or shooting himself. Superman tries to talk him out of it and almost succeeds when the employee unexpectedly shoots the hero instead. It is then revealed that the suicide ploy was meant to trick Superman into lowering his guard, that the former employee was impersonated by Metallo and that the bullet was made of kryptonite, the only material that can harm the hero. A fatally wounded Superman falls from the top of the building.
Batman comes close to accepting his fate but, motivated by the memory of his father's murder, is able to dig his way out of the grave. He soon realises that the League has been attacked using his own contingency plans. With help from Cyborg, he saves his teammates one by one.
The Justice League retreats to the Watchtower, where Batman reveals that he was the real mastermind behind the attacks, having studied the others for physical and psychological weaknesses. He also reveals that he had a contingency in place should the Batcomputer ever be hacked: a tracing algorithm hidden in his files. This enabled the League to track down the Legion of Doom.
The villains are subdued, but the heroes fail to prevent Savage's scheme to orchestrate an apocalyptic cataclysm with a powerful solar flare. Using information obtained by Cyborg, Batman devises a last minute plan and the League barely manages to save the Earth. The World Court sentences the immortal Vandal Savage to life imprisonment without possibility of parole.
In the aftermath of their victory, the Justice League votes to add Cyborg to their roster. Superman calls for a vote on Batman's continued membership in the team, following the revelation of the latter's breach of trust. Batman defends his plans and expresses no regret over his actions, ultimately resigning voluntarily.
In the final scene, Superman entrusts Batman with the kryptonite bullet but not without first questioning him about Bane's attack. It is revealed that exhuming the bodies of Thomas and Martha Wayne was Savage's idea, but that Batman did have a contingency plan in place should he himself go rogue: "It's called the Justice League."
- Superman - Friend and teammate.
- The Flash - Teammate.
- Wonder Woman - Friend and teammate.
- Martian Manhunter - Teammate.
- Animation (1 film)
- Justice League: Doom - Kevin Conroy