Synopsis
It is the year 20XX in a flooded Manhattan. The Golden Skull's gang has just stolen a shipment of helium when they are attacked by a female black Captain America. She's Danielle Cage, the daughter of Luke Cage and Jessica Jones, and she's inherited their powers. She also has a version of Cap's uniform and round shield, which seems to attach to her arm by magnetic clasps. Later we will learn that it is a though-controlled anti-gravity shield.
However in the middle of taking the gang down she disappears through a glowing square - to everyone's surprise.
In present-day Avengers Tower Black Widow and Vision are supposed to be training together. Natasha Romanoff weaves through a web of lasers to hit the android with her Widow's Bite. But he just increases his density and continues drinking his coffee and reading a paper. He claims his diagnostics tell him he's in peak condition so he doesn't need to train. He tries to turn it into a joke, ending with the paraphrase "Even an android can laugh".
They get into a discussion of 'programming', comparing his android makeup with the brainwashing and intensive training she endured in the Soviet Red Room program. But then the glowing square claims them, and Vision drops his coffee and paper. The headline has the UN complaining about Dr Doom's temporal experiments.
And they find themselves indeed facing Dr Doom. As well as the female Cap there are other time-lost Avengers. The female Thor is beside the male Thor from Walt Simonson's stint on his book. Iron Man is actually James Rhodes. And Hulk is the pre-Avengers version.
Doom says he has gathered the 6 of them here with his time squares to prevent mankind's extinction. (It seems Vision is an unintended bonus.) But Hulk doesn't listen and immediately attacks. The other Avengers don't trust Doom, so they join in as well. The power of 2 Mjolnir's is enough to overload his forcefield, letting Iron Man through. But Vision holds Black Widow back - he thinks things aren't what they seem because he recognises Doom (ie as someone else).
Iron Man's assault is stopped by a horde of children who declare Dr Doom is their protector - followed by an old man Marek who is supposed to be looking after them.
The Avengers use the lull to greet each other. Hulk is surlily unhappy about everything, especially Widow automatically taking charge. Danielle introduces herself to her heroes. It turns out that the female Thor is from a little way ahead in time, and has to be stopped from telling the others things they don't know (she specifically mentions a Qeng Dynasty). The male Thor assumes he has died in the future and is glad there is a worthy successor to carry his hammer. Fem-Thor won't burden him with the knowledge that he isn't dead, just no longer worthy.
Dr Doom tells them that Earth has been subjugated by the Ultron Singularity. In 2420 the Ultimate Ultron killed all the superheroes. He has converted most of humanity to mindless bio-slaves. His factories create Ultron-drones to spread out and conquer the universe. And he has built AI's in the shape of Avengers. Natasha says she visited this future in Avengers #31 (as part of the extended time-trip in the Original Sin tie-in issues #29-34).
Future-Cap says that Doom has died in her time, so she doesn't know how he got here - and doesn't trust him whatever the circumstances. Vision makes it even more clear that he knows who Doom really is, but Doom still insists he's the one true Dr Doom. Vision won't betray Doom's secret, but assures his fellows that they can trust him. The others agree to grudgingly follow Doom's plan.
As usual in jaunts like this the Avengers are split into teams to tackle what Doom claims are Ultron's weak points - caused by the still-human basis of his thought patterns.
The robot villain has concentrated control of all his factories in Avengers Tower. Iron Man and Vision are sent to destroy it. (And we get a reminder of very old times as the Golden Avenger travels by built-in roller skates.) They take out some Ultron-drone guards, but are then attacked by the AI versions of Captain America, Hawkeye, Spider-Woman and Vision himself. In particular the evil Vision uses his own phase-an-arm-through-the-chest trick on 'himself'. He claims to actually be the original Vision subverted by Ultron, but doesn't remember this encounter.
Black Widow, Captain America and Hulk are sent to another central control system, which broadcasts the instructions to the human bio-slaves. They use stealth to get in (so why has Hulk been sent with them?). They can't just let Hulk trash the place because then a backup system would take over. They have to disable the backup system 1st.
Widow also says she doesn't want to risk Hulk getting killed because he is necessary in his own time for the formation of the Avengers. However they are found by the AI Black Widow and a bio-slave army. In the ensuing fight AI-BW grabs Cap's shield and uses it to cut Hulk's head off. So much for protecting history.
Meanwhile the 2 Thor's have gone to Ultron's homebase, which turns out to be Asgard and the Rainbow Bridge brought to Earth. They are met by the AI Thor who taunts male Thor by revealing that he loses Mjolnir by being unworthy to wield it. And it was his absence that allowed Ultron to take Asgard and reign as the All-Father. Male Thor attacks enraged, ignoring female Thor's warnings of caution, and AI Thor runs him through with a big sword.