Lex Luthor is running for president, but his poll figures are terrible. He learns that the Joker knows how to produce more Kryptonite, and can make a gas that makes people love him, which will help Luthor win the election and defeat Superman. He breaks the Joker out of Arkham Asylum and promises him the use of Luthor's De-Constructor weapon to defeat Batman by dismantling all his shiny black toys.
Batman and Robin investigate the breakout, which leads them to Ace Chemical, booby-trapped by The Joker after a visit to gather materials for the gas and Kryptonite. Superman rescues the Dynamic Duo, but Batman is rude to him (concerned he might go rogue some day) and he leaves. Batman traces Luthor's mobile lab and snatches the manufactured Kryptonite, but the Batmobile is deconstructed. At the Batcave, he determines the new Kryptonite is harmless, but it proves to be a tracking device which leads Luthor and Joker to the cave—Batman has a Kryptonite Vault, which The Joker knew about. Using explosive pies, the villains destroy the cave, escaping with a load of Kryptonite, while the heroes are saved by Superman.
The next day, election day, Superman and Batman visit the LexCorp building, and are attacked by Luthor in a giant Kyrptonite-powered Joker robot. The villains describe their plan to the heroes as they defeat them, and then leave. However, Batman and Superman had switched costumes to learn Lex and Joker's plan. The two then switch back costumes and chase down the robot, but fail; since the Kryptonite drained Superman's powers and Batman doesn't have a vehicle, the two are forced to take a bus to City Hall. Later, outside City Hall, Lex makes a speech in front of a huge crowd and then has Joker use the Joker robot to spray the crowd with Joker Gas. Lex then finds out that the Joker Gas has caused the crowd to start cheering for Joker to be president and realizes Joker tricked him. Joker's handiwork is visible from space, alerting the Justice League, who arrive to help Batman, Robin, and Superman.
After a prolonged battle, the League traps the Joker robot. Cyborg and Batman open up the robot's chest with explosions, and the Flash loads the Kryptonite into Wonder Woman's invisible jet. Cyborg offers that the League help rebuild the Batcave. Batman at first refuses, but Robin convinces him to accept their offer. Green Lantern then fires a bright green light into space to celebrate their victory.
From his ship deep in space, Brainiac spots the green light and realizes that he just found Earth.
- Clancy Brown as Lex Luthor
- Troy Baker as Bruce Wayne / Batman, Two-Face, and Brainiac
- Christopher Corey Smith as the Joker
- Travis Willingham as Clark Kent / Superman
- Laura Bailey as Harley Quinn, Poison Ivy, and Wonder Woman
- Brian Bloom as Cyborg
- Steven Blum as Bane and the Penguin
- Cam Clarke as Green Lantern and J'onn J'onzz / Martian Manhunter
- Townsend Coleman as Commissioner James Gordon
- Rob Paulsen as Riddler
- Charlie Schlatter as the Flash and Robin
- Katherine Von Till as Catwoman and the voice of the Batcomputer
- Erin Shanagher as News Reporter