As the final part of King Kull's plan continues, the three groups of heroes, the JLA, JSA, and Squadron of Justice, unite to stop him.
The Golden Age Flash and Green Lantern, the Silver Age Flash and Green Lantern, Ibis, the Invincible, and Mercury, Roman Messenger of the Gods, attack Mister Atom. Mister Atom is attacking the city of Tomorrow, an experimental habitat. Mister Atom is protected by a black aura that repels all the heroes attacks. The Golden and Silver Age Green Lanterns, and Ibis, the Invincible, coat themselves in the same black aura surrounding Mister Atom. The Golden Age Green Lantern detects the power source for the black aura. Unable to penetrate Mister Atom's defense, the Golden and Silver Age Flashes, and Mercury, are kept busy rescuing Tomorrow's inhabitants.
People begin falling skyward, leading the Silver Age Green Lantern to suspect the involvement of Doctor Destiny. The Golden And Silver Age Green Lanterns, and Ibis, the Invincible, rescue the ascending civilians. Brainiac, not Doctor Destiny, is revealed to be Mister Atom's partner. The Silver Age Green Lantern storms Brainiac's spaceship, only to be transformed into a living skeleton. Ibis, the Invincible, incapacitates Brainiac. The Silver Age Green Lantern is restored to normal. Interrogating Brainiac, the Silver Age Green Lantern learns that Mister Atom's attack on Tomorrow is designed to force the three super-speedsters to keep running.
The Silver Age Green Lantern destroys Brainaic's ship's systems, shutting down Mister Atom's black aura. The Golden and Silver Age Green Lanterns destroy a device, which was using the super-speed energy expended by the three super-speedsters, to speed up the rotation of the Earth, cancelling gravity's hold on the civilians. Ibis, the Invincible, confronts Mister Atom, only to be instantly struck down. Mister Atom pick up the Ibistick and commands it to hurl Ibis, the Invincible, into the heart of a star. Due to a failsafe that prevents anyone other than Ibis, the Invincible, from commanding the Ibistick, Mister Atom is hurled into the heart of a star.
The Justice League of America, the Justice Society of America, and Shazam's Squadron of Justice storm the Rock of Eternity, to confront King Kull. King Kull exposes Superman to red kryptonite, transforming Superman into a murderous berserker. Johnny Thunder meets with Freddy Freeman, and Billy and Mary Batson. Johnny Thunder summons his Thunderbolt. The Thunderbolt takes the place of Shazam's magic lightning, transforming the Batsons, and Freeman, into Captain Marvel, Mary Marvel, and Captain Marvel, Jr. The Marvel Family storms the Rock of Eternity. Captain Marvel, Jr destroys King Kull's technology. Mary Marvel releases the Olympian Gods from their torpor.
Captain Marvel beats the living daylights out of KIng Kull. The Golden and Silver Age Green Lanterns pelt Superman with kryptonite. Exposure to red kyrptonite, however, has given Superman immunity to green kryptonite. Captain Marvel closes on Superman. A moment before impact, Captain Marvel screams the word "Shazam", triggering Captain Marvel's transformation back into Batson. The magic lightning also draws out the red kryptonite radiation poisoning, restoring Superman's rationality. Superman rescues Batson from a life threatening fall. With King Kull in chains, and the crisis over, the heroes of three Earths return home.