Some strange force has caused people on both Earth-One and Earth-Two to suddenly switch worlds. While Dr. Mid-Night and Black Canary are transported to Earth-One, Batman finds himself transported to Earth-Two. To make matters worse, the Spectre is drawn to the Anti-Matter Man, the being responsible, and Solomon Grundy is freed from his mystical prison and transported to Earth-One, while Blockbuster breaks free of the Alfred Foundation and finds himself transported to Earth-Two. While Green Lantern, Hawkman, Flash, Dr. Mid-Nite and Black Canary gather at JLA headquarters, Ray Palmer cannot change into the Atom to join them because he is in the middle of a research project with a colleague. While the JLA/JSA members on Earth-One battle the threat of Solomon Grundy, Batman meets up with Dr. Fate, Sandman and Wildcat on Earth-Two where they pit their might against Blockbuster. While on Earth-One the heroes manage to trap Solomon Grundy beneath the Earth, the heroes on Earth-Two manage to defuse Blockbuster's rampage when Batman removes his mask -- as Blockbuster associates Bruce Wayne as a friend. While the Spectre faces the Anti-Matter Master alone, and learns that this creature is the cause of all the disorder on both Earth's, and that its continued approach will cause the worlds destruction. Defeated in combat by the Anti-Matter Master, all the Spectre can do is use all his mystic power to keep the two Earth's separated.