Synopsis
The previously page shows the Illuminati preparing to delete Captain America's memory of the incursions of alternate Earths in New Avengers #3, and Cap getting those memories back in #29. Iron Man merges the rogue planet with Earth in #24. The Cabal meet Reed Richards on Ultimate Earth, and Gladiator decides to send an alien armada to destroy Earth, both from #41.
Now we flash back some months to Steve Rogers and Tony Stark meeting in an out-of-the-way burger joint in Texas. Tony is making another effort to persuade Steve that what he and the Illuminati did was right. Steve says he'll listen - but then the SHIELD guards outside will arrest Tony.
Rogers accuses Stark of pride in not considering that his plans might fail. Stark responds that failure in this case would mean the death of everything. He thinks they should join forces to stop the Cabal. Steve says that the Cabal are just doing what the Illuminati did. (Not strictly true. Jonathan Hickman carefully arranged that the Illuminati didn't destroy any populated alternate Earths until Sub-Mariner personally wiped out the Great Society's Earth in NAv#21. Then Namor founded the Cabal to continue the work. It could be better put that the Illuminati built the weapons that the Cabal use, and Steve believes they themselves would have used them eventually. [But NAv#21 suggests he was wrong. If it wasn't for Namor the universe would have been destroyed then and the question would no longer apply.])
Tony draws Steve's attention to their waitress, and Steve realises it is Tamara Devoux. As usual Tamara doesn't know about being Captain Universe, but she seems mentally stable now and has her young daughter with her. Tony says he found the missing (see #6) daughter for her.
This softens Steve's attitude, and Tony tells him that together they can solve all the problems. But Captain Universe suddenly takes over Tamara and tells Stark to stop lying. He built the current Avengers with a promise like that, but the universe is dying and he knew that from the start.
Now we return to the current situation where the various Avengers teams (including Hulk) are all united against the threat of destruction by the alien fleet. Last issue the Illuminati swapped Earth for the out-of-phase rogue planet, so it is that which now faces the armada. Iron Man is on the partial Dyson Sphere he built round the Sun (NAv#4) and uses it as a weapon - Sol's Hammer. The solar blast knocks a chunk off the Moon before ripping through the alien ships. And then it strikes the rogue planet without harm (at least to the out-of-phase Earth).
The Dyson Sphere is also destroyed, Earth is swapped back into phase, and Iron Man heads home.
Now we go back in time a bit in the Ultimate Universe. Hawkeye and Nick Fury come to the City at the call of Reed Richards. Richards tells them he's been secretly stopping incursions of alternate Earths and thereby saving their universe. He takes them to meet Maximus and Thanos of the Cabal who have come from the main Marvel Universe (#41). They confirm Reed's story of the incursions.
But Reed can give Barton and Fury some evidence. He causes the whole City to rise into the air and travel to a current incursion site. Once inside the periphery the sky turns red and the astonished Hawkeye and Fury see another Earth in the sky. And watch as Richards destroys it with a missile - and the incursion ends.
Thanos explains the problem in more detail. In an incursion the other Earth must die to save the universe. He goes on to say that there are now only 2 universes left in the whole multiverse. The other is the 1 he came from (Marvel Earth). That world is full of superbeings, but Ultimate Earth must kill them all to survive.
Back on Marvel Earth in current time Black Panther visits the President and tells him the world is going to end today. The Avengers are working on a method of saving a few people (and a lot of information) to possibly restart the human race afterwards. The Pres says surely someone must be able to save the world. T'Challa can't resist getting in a dig about how Wakanda might have been able to do something, but the US and the UN gave his country to the Cabal. The attending General typically thinks this is all a threat and offers to attack the Avengers to stop them.
At the same time on Ultimate Earth Thanos and Sub-Mariner are watching Maximus prepare for the final incursion. Nick Fury is part of their plan. Maximus believes Fury knows they lied to him, but with his world at stake he won't have a choice. Nick addresses SHIELD troops in the Triskelion. He offers them each the chance to go home to be with their familes. Meanwhile the City arrives to join them.
On Marvel Earth Mr Fantastic and Invisible Woman hold a meeting in the Baxter Building with Beast, Captain Marvel, James Rhodes and Steve Rogers. Reed says the Illuminati have built a spaceship they hope can survive the collapse of the multiverse. Still-angry Steve doesn't want any of the Illuminati to be given that escape route. Sue Richards argues that some of them will be useful. Bruce Banner and Brian Braddock have declined, and Henry Pym's mind has been affected, but the others should go. Captain Marvel agrees.
But the problem is Tony Stark. Beast and MrF say they'll need his engineering smarts. But even Tony's best friend Rhodey doesn't trust the Superior version. Sue agrees. And Steve is adamant that Stark doesn't deserve a place on the lifeboat. In fact Rogers' last act before the end will be to seek out Stark and kill him, if James Rhodes will tell him where he is.
Tony is in some place called the Resurrection Building, Stark Underground (that we've never seen before). The final incursion is 4 minutes away when he detects the approach of some of Rhodey's War Machine drones. 1 of them enters the building but it's not Jim, it's Steve Rogers in Stark-designed battle armour.
The fight begins. All through it their conversation riffs off flashbacks to the beginning of #1 where Tony told Steve his vision of the upgraded Avengers. (We realised later in NAv#3 that this was the morning after Cap had certain memories wiped by the Illuminati.) Gradually bits of armour get knocked off.
As the sky truns incursion-red, Steve wants Tony to admit the truth of what Captain Universe said. That the latest Avengers were a sham. Stark knew it was all futile and he lied to everyone. And as Rogers finally gets the upper hand, Stark admits it all. But he says they had to try something, and he'd do the same thing if he was given it all to do again.
The issue ends with with the quote from the end of #3 "It started with 2 men. 1 was life and 1 was death ...." and it completes it with "... and 1 always wins." followed by the NAv mantra "Everything dies." As the 2 heroes continue to fight, the war between Marvel Earth and Ultimate Earth begins.