Synopsis
Centuries in the future Ultron has taken over the world but now Dr Doom, with the help of some Avengers plucked out of his past, has taken over the take over. He controls spy satellites, the bio-slaves (most of the human population), the Ultron drones (whose heads have now changed from Ultrons to Doom masks) and a fleet of flying fortresses (again with his own mask on the front).
He tried to send the Avengers back to their own times at the end of the last part, but the 2 Thors transported them elsewhere. Doom knows they have gone to the current-day Asgard (hovering above the Earth), from where Ultron ruled until his defeat last time.
The Avengers are:- Black Widow and Vision from our present. Hulk, Thor and the James Rhodes Iron Man from our past. Female Thor and Danielle Cage/Captain America from our future. In Asgard they meet up with the current Thor who they freed from Ultron's control in the last part.
In part 1 Vision persuaded his compatriots to trust Doom. Now he wants to try to solve the problem by talking to him. The other Avengers suspect his android brain may have been taken over. Unable to convince them otherwise Vizh ghosts away.
They ask current Thor if the other Asgardians will help them. But he shows them a magic mirror where Loki has imprioned them. And it drains their Asgardian powers so they can't escape. And it is impregnable to Asgardian might or magic from this side too. Before they can try any other ways of breaking the spell a Doomship arrives and starts spewing Doom/Ultron drones. All the heroes rush out to fight the foe except Iron Man who thinks he can smash the mirror.
Danielle Cage has grown up to be the future Captain America. Hulk is from the beginnings of the Marvel Age before he joined the Avengers. Currently he is in the unusual state of having Bruce Banner's head sprouting from 1 shoulder. Danielle asks Hulk to use a 'fastball special' to get her into the Doomship. Banner doesn't understand the reference to the technique pioneered later by Colossus and Wolverine in the X-Men, but Hulk gets it immediately. And he hurls Cap through the air and through a window into the control room of the flying craft.
Doomtrons try to disrupt the antgravity device in her shield. But she has it switched off and relies on her strength and invulnerabilty (inherited from father Luke), and her skill and the shield's sharp edge, to defeat the 'bots. And she gets help from Vision who ghosts in to stop a Doomtron from setting off lethal radiation. It turns out that there are 2 other Doomships in the attack, so Cap and Vizh take control of their ship and destroy 1 of the others.
Down on the ground the 3 Thors are laying waste to Doomtrons. Female Thor and the Simonson-era armoured Thor use their hammers (the same Mjolnir from 2 different times), while the still-unworthy-to-wield-Mjolnir future Thor uses a sword. They notice that the unwieldy 'friendly' Doomship is caught with its flank exposed to the 3rd battleship. Until 2 hammers and a blast of sword energy take that 1 down.
Meanwhile Hulk is doing his own bot-smashing while Banner tries to avoid getting his head damaged. And Black Widow shelters behind 'them' taking out Doomtrons with her wrist blasters.
Back in Asgard castle Jim Rhodes has figured out how to communicate with the Asgardians behind the mirror. Their speech comes through in reverse. so he gets his suit computer to 'translate' for him, and transmit his own words in reverse. Beta Ray Bill says his hammer Stormbreaker is solar powered. It is obvious that the mirror lets light through, so Rhodey aims a powerful laser blast at Stormbreaker. And Bill smashes the mirror from inside.
As the ground battle continues, other Doomtrons start to break into Cap and Vizh's Doomship. Vision sends Danielle to help with the fight below, while he crashes the ship into a mass of 'bots. But then lots more loaded Doomships turn up. But so do Iron Man and the Asgardians. Cue 2-page battle-spread.
Hulk and the Asgardians are tireless, but Widow and Cage are getting exhausted, and Shellhead is running out of power. But then Vision reappears and suggests they try another tack, before Earth is completely devastated. He asks them, especially his contemporary Natasha, to trust him. And the Thors transport them to Dr Doom's HQ.
There Vizh addresses 'Dr Doom' as a Doombot. But not just any Doombot, but the Doombot who was a member with Vision of the Avengers AI team. He asks what turned him back from the road of the hero. The Doombot says that when the real Dr Doom died a backup of his mind activated in the 'bot to continue his legacy. Vision asks which legacy he is honouring:- Doom the power-mad conqueror or Doom the protector of his people. The Doombot says he must follow his programming - and Vizh repeats a point from the 1st part, that humans are as programmed as AIs and AIs are as free as humans. Besides, Dr Doom would never slavishly follow orders even from himself.
His argument wins out. The Doombot frees the mind-slaved humans and in the future allies with Asgard to develop humanity into a spacefaring society. Meanwhile the Avengers are returned to their home times. Vision says he didn't tell them Dr Doom was a Doombot initially because they would have still treated him as an enemy. Widow says he could have tried trusting them to make the right choice. And Cap gets to finish capturing Golden Skull (from part 1) - and we see her Avengers team.