In Gotham City, Batman chases down a serial killer responsible for murdering twelve children. Confronted by his own guilt, the man throws himself from the roof of a building. Batman is unable to save the man, owing primarily to the sudden and distracting appearance of the Martian Manhunter. Something is affecting the Manhunter's perceptions, and he begins lashing out wildly. Batman calms him down and brings him back to the Batcave. J'onn is feeling better, but confesses that he has recently been ill and experiencing bizarre hallucinations. One of J'onn's hallucinations manifests itself in the Batcave, and Batman notices it as well. The image is of a monstrous, amorphous, black demon. J'onn loses his composure and knocks Batman out before fleeing from the cave.
Later, the Martian Manhunter continues to struggle with the demonic villain, and the two exchange blows. J'onn is still convinced that this manifestation is just a byproduct of a fever dream.
Meanwhile, Batman goes to the JLI embassy in New York to confer with his teammates in the League. He warns them all that measures will need to be taken to control the Martian Manhunter.
— Description from Comic Vine community (comicvine.gamespot.com).
