Justice League of America, Vol. 1

Superman is on his way to the Daily Planet in Metropolis to meet with his pal Jimmy Olsen, however when the Man of Steel arrives he suddenly loses all control of himself, crashes into the ground and falls unconscious. Superman is then brought to the JLA satellite by Hawkman, Atom, Flash and Batman to be examined and determine what befell their comrade. Batman then is also knocked out just as suddenly as the Man of Steel, prompting Hawkman and the Atom to call in Green Lantern, Green Arrow and Black Canary away from their leaves of absence to answer this new emergency.

Unknown to the Justice League of America is that their problems are coming from Earth-Two, home of the Justice Society of America. Things began when the Red Tornado is captured by alien creatures led by a being known as Creator2 who hopes to merge both Earth-One and Earth-Two together into one planet. They capture Red Tornado (a being with origins in both universes) to use as an anchor to cause the vibrational barrier between both universes to crumble. Knowing the only opposition to their goal would be the Justice Society of America they send out troops to incapacitate the heroes, their actions would also cause each victims Earth-One counterpart in the Justice League also incapable of resisting this plot. They initially run into Superman and Dr. Mid-Nite who are on their way to a JSA meeting and because they are incapacitated, Earth-One's Superman and Batman (their dimensional counterparts) to be incapacitated as well.

The aliens then run into the Earth-Two Flash who tries to stop them as well, but despite his super-speed he too is knocked out, causing his Earth-One counterpart to become inert as well. Meanwhile, channeling energies through the Red Tornado causes the barriers between universes to slowly decay, and slowly people from Earth-Two begin to materialize on Earth-One before their alternate reality counterparts. The crisis causes all the JSA members to meet up and try to an investigate the weird happenings. While on Earth-One, Green Lantern (who has his powers restored by the Guardians while this crisis is afoot) arrive with a begrudging Green Arrow and Black Canary to figure out what's happening down on Earth.

When the Atom's computations and Green Lantern's physical investigation tell that it's due to a destabilization between Earth-One and Earth-Two, they deduce that someone unique to bother realities may be the source. Unaware that Red Tornado is the source, Black Canary figures that it's due to her crossing over into Earth-One. The Black Canary then begins to believe that in order to save both Earth-One and Earth-Two she must sacrifice her life.