Enrichetta Negrini operates a device to warp space, allowing mankind to teleport between planets. Unbeknownst to Negrini, her device has put Earth-1 and Earth-2 on a collision course. It has also opened a rift in space, allowing the Anti-Matter Man passage into the universe. The device is also keeping physicist Ray Palmer from activating the powers he uses, as the Atom. Palmer turns off Negrini's device, restoring his powers. On Earth-2, the Batman keeps the Blockbuster subdued, by exposing his unmasked visage. Suddenly, the Blockbuster vanishes, only to be replaced by Solomon Grundy. Immediately, Solomon Grundy lashes out at the Batman, and the Justice Society of America.
The insane hatred Solomon Grundy harbors, towards the Golden Age Green Lantern, causes him to hallucinate that the Golden Age Green Lantern is everywhere. On Earth-1, the Blockbuster reappears, taking Solomon Grundy's place within a mountain prison. The Blockbuster breaks out, immediately attacking Solomon Grundy's jailers, the Justice League of America, Doctor Mid-Nite, and the Black Canary. While the Justice League of America and the Justice Society of America are engaged in combat with the Blockbuster and Solomon Grundy, on their respective Earths, Doctor Fate becomes aware of a greater crisis. Earth-1 and Earth-2 are on a collision course, and the only thing keeping the worlds apart is the power of the Spectre.
To make matters worse, the Anti-Matter Man is fast approaching the Earths. Doctor Fate gathers the Justice League of America, and the Justice Society of America, to his side, to confront the greater threat. Before they depart, the Silver Age Green Lantern takers steps to keep the Blockbuster, and Solomon Grundy, occupied in the heroes' absence. With the Spectre physically holding Earth-1 and Earth-2 apart, the Justice League of America and the Justice Society of America confront the Anti-Matter Man. An epic battle ensues Ultimately, the Justice League of America, and the Justice Society of America, triumph over the Anti-Matter Man.
With their foe momentarily subdued, the Justice League of America, and the Justice Society of America, push the Anti-Matter Man further out into the dimensional void between the two Earths. There, their epic battle continues. Using Negrini's device, the Atom becomes aware of the Spectre's dilemma. The Atom teleports to the Spectre's position. The Atom shrinks the Spectre down to an inch in height. Shrinking down to sub-atomic size, for safety, the Atom then re-enlarges the Spectre. The rapid re-expansion of the Spectre's molecules causes the Spectre to explode. The shockwaves of the explosion are so powerful, that Earth-1 and Earth-2 are pushed back into their proper dimensional space. The Anti-Matter Man is also hurled back into his own universe.
After the Spectre reforms, he and the Atom join their teammates. The Silver Age Green Lantern reveals that he brought Solomon Grundy and the Blockbuster together, so they'd spend all their time fighting each other. Astonishingly, the heroes discover that the Blockbuster and Solomon Grundy have impossibly beaten the hate out of one another. Now the best of friends, Solomon Grundy and the Blockbuster embrace their former foes in the Justice League of America and the Justice Society of America. Solomon Grundy returns to Earth-2, with the Justice Society of America. The Justice League of America return the Blockbuster to the Alfred Foundation. The Justice League of America, inexplicably, decide not to tell Negrini that her research into warping space, nearly culminated in the destruction of two worlds.