Batman: Finally, after eight issues, said plain exactly what the heck had been going on. "Earth and the planet Rann are under attack by mystical forces... demons inhabiting long-dead human beings, and creatures risen out of ancient mythology. At the same time, Earth is being invaded by aliens from some cosmic organization called the Greater Galaxies... I found three 8-figure numbers scrawled on a wall at a power plant... I ran these numbers through my computer here in the Batcave... and got a result that seemed to spell a formula to bring about the end of the world. The numbers, decoded, are electro-magnetic vibrational frequencies... [if] put into operation... the resulting wave-front could crack the Earth like an eggshell." The Dark Knight Detective knew demons were involved, and headed in his Batplane for their nearest concentration point, Metropolis. In the distance, a warp hole opened. "I'm too late... the Batman has already departed. Pity. I might have been of some assistance."
Unbeknownst to the Dark Knight, his nemesis the Joker had helped orchestrate attacks on Earth's heroes with the Greater Galaxies organization. The Clown Prince of Crime worked under the turbaned alien Kaz with the promise of kingship over Earth. Kaz explained the situation as follows:
"Project X involves the disruption of physical reality... the merging of this reality-plane with that of the netherworld. Bork and his fellow renegades of the Black Council have discovered a weakening of the cosmic fabric here in this locus... on the world you call Earth. A similar, parallel weakening is taking place on the planet Rann, of the star-system Alpha Centauri.
Bork has developed a device known as the Probability Disruptor, which feeds on red sun radiation, relayed to this world from a base on Earth's satellite, Luna. The Disruptor is destroying the protective barrier between realities at this locus. The result is an increase in the manifestation of demons on Earth... manifestations that occur normally at this locus, at periodic intervals related to phases of the moon. Bork's disruptor, however, has increased the number of manifestations a thousandfold.
Project X is upsetting the natural cosmic balance... a balance we of Molanto have worked long and hard to maintain. To save reality, Molanto, in conjunction with the Greater Galaxies organization, have invaded Earth. We have done this for the simple reason of expedience. Bork must be found. Project X must be halted. The fastest, simplest way to accomplish this is through the conquest of Earth."
Martian Manhunter: Earth's super-heroes were likely to interfere, so Kaz engaged the Joker to assist in distracting them. The Joker stated, "Capturing all the heroes who'd been born off world, like Superman and J'onn J'onzz, among others-- and threatening to execute them as traitors to the Greater Galaxies-- that was my lovely idea. See, it's what we call a red herring. Now all the other heroes will be wondering what the alien heroes have to do with the alien invaders. It'll drive 'em nuts, giving us time to strike! Which brings me, oddly enough, to my final plan... I need three million tons of rubber cement, Kaz..." The Joker wanted to gum up the works in Washington. D.C., but Kaz was done with this insanity, and had the Joker locked away.
Batman: The Batplane flew over Metropolis, which by this point looked, as Batman put it, "like something out of Fantasia's 'Night On Bald Mountain!' Demons everywhere... as if a doorway had opened between our world and Hell!" The pandemonium led to the destruction of the Batplane, but the Caped Crusader still managed to reach the Galaxy Broadcasting Building, now aware thanks to the infernal beings he had been inadvertently helping this "Kaz" person.
The Dark Knight was met by Dr. Terrence Thirteen, Ghostbreaker and Floyd Perkins, the kid who started this all in the first issue. Perkins had told Dr. 13 about finding a floor in the building that shouldn't exist, and bumping into an undead Humphrey Bogart. Dr. 13 in turn told Batman about his and Superman's Pal Jimmy Olsen's running into the alien invasion, and through a space-warp into the Plane of Holes, where they met Darwin Jones and Bobo the Detective Chimp, among others. Dr. 13's memory was fuzzy after that, recalling that he had been returned to Earth by Albert Einstein, but decided to pick up the investigation again. Doctor 13 had brought a radiation detector with him, and when Batman had a look at the frequencies emitted from the GBS antennae, he recognized them from the earlier inscriptions! Dr. 13 had backtracked his detector's readings to their source, the moon...
Batman called on the Outsiders, but they stopped short of the Galaxy Building to address the demons running rampant throughout Metropolis in Superman's absence. Batman predicted the end of the world as the signal from the moon began shaking Earth apart, and a whole building began to fall on the Outsiders...
"If This Is Love, Why Do My Teeth Hurt" was by Gerry Conway, Rick Hoberg, Dick Giordano and Arnie Starr. This was the tidiest, most descriptive issue to date, and even managed to work its gonzo title into the narrative (lovers kissing as the world begins to vibrate violently.) Detroit co-creator Conway missed writing the rest of his team in the next issue...