Synopsis / Summary / Plot
Mercenaries working for the deposed rulers of Slorenia, the Tabissaria, against the new democratic government are opposed by what they think are US drone planes. But when they shoot 1 down they find that, although it does have US markings, it's some giant cyborg creature.
Captain America prepares for the weekly Avengers meeting in Avengers Tower, still not comfortable having his coffee made for him by a butler, Jarvis. But then he's not comfortable with a lot of the modern world.
Captain Marvel is the 1st to arrive, and she engages in some interservice rivalry banter with Cap (Air Force vs ex-Army). And she reports that medical tests have shown that her human/Kree hybrid situation is still stable.
Black Widow and Wolverine turn up, and Iron Man arrives on the roof. And Hawkeye staggers in after a night on the tiles.
Steve Rogers hears a news report about the Slorenia incident. The cyborg technology is unfamiliar to defence experts. But as well as the US markings the 'drone' has Hereward painted on it, which is the name of a British military contractor based on the Norwegian island of Skrekklandet. And this causes Cap to flasback to a wartime mission.
It's 1944 and Cap was with a trio of RAF bombers sent to the island. Cap intended to parachute down to investigate before calling the planes in to bomb the place. He suspected Baron Zemo was there, building wunderwaffe (wonder weapons). Suddenly 1 of the planes was destroyed by a beam from above, from a huge delta-winged craft.
Cap ordered his plane to fly above the mystery craft and launched himself down on to it. (As he did so, lightning struck the island base below them.) Cap smashed into the cockpit with his shield, and threw a bunch of live grenades in. Then he abandoned the stricken craft to regain his own plane.
But then a beam much like the one that hit the 1st plane struck the island. And the base was reduced to a crater,
Back in the present, Steve wants to know what's happening. The team cease exchanging friendly insults and snap into action. Tony Stark pulls up more details of the attack in Slorenia, while Cap explains about his 1944 mission and says the tech there reminds him of stuff he fought in the war, and stuff Red Skull used later. Meanwhile Carol Danvers finds out from the Air Force that the things aren't remotely-piloted drones, they're semi-intelligent machines. And the US has subcontracted the whole operation to Hereward. Natasha Romanoff gets SHIELD info which indicates that Hereward is active worldwide, gaining power and influence.
Logan figures correctly that Steve wants to get hold of 1 of these 'drones'. Storming Skrekklandet would be frowned upon, but getting into the Slorenian war zone will be easier. Even though Colonel Danvers protests that's still against US policy. Later Cap tells Widow they're taking the job because SHIELD and other official US agencies won't.
Thor joins the gathering, and is reminded of something from his past too. There is an evil creature called Nidhogg that lives among the roots of Yggdrasil the World Tree that supports the Nine Realms of Asgardian lore. One day it escaped to 1 of the Realms, Midgard - Earth. (We see it surfacing at the Skrekklandet base with the delta-craft flying overhead.)
Thor tackled it alone, his arrival signalled by a lightning strike. Nidhogg had laid eggs in the ice. Thor and the monster fought, and Thor was driven to Berserker Rage. The battle ended with a massive beam of energy wiping out the base.
Thor's pride in going it alone, and succombing to the Rage, convinced Odin that his son needed to be taught humility.
Now Thor recognises the fleshy base of the cyborg 'drone', and suspects that it is a spawn of Nidhogg. Stark reasons that the 'drones' are the result of Nidhogg's children fusing with the Nazi experimental weapons after being buried by Thor.
Thor's humility lesson doesn't seem to have taken, because he wants to go hunt the creatures alone again. But Steve says this kind of thing is why the Avengers were formed. (And reminds them that they've all gained from the association, even Thor.)
Wolverine suggests they just drop Hulk on the enemy. Black Widow reminds him that Bruce Banner now works for SHIELD, with drugs to keep his Hulk side down.
When they get to Slorenia they detect 2 active 'drones'. Thor goes to capture one, with Captain Marvel and Iron Man, while the rest fly the quinjet to the launch site within the country.
IM deploys something to hide their activity from prying eyes. CM and Thor double-team the creature they have chosen, knocking it out. And IM attaches lines to it, to haul it away.
When Cap's group get to the launch base they find it in a mess. BW and Logan grab a techie who tells them that the Ice Harriers (as it seems they are called) still at the base went mad, smashed up the place, and started burrowing into the ground. Remote detonators have killed 1 of them and the airborne 1 that Thor's team haven't got. But there are 2 underground that aren't affected.
One of those creatures now bursts out of the ground. Only to be taken out by a bunch of delayed-explosion arrows from Hawkeye.
Wolverine notes that the last Ice Harrier is spawning in its hole. BW calls for something inflammable to burn them with. (But we don't actually see the result in detail.)
However the problem isn't over. The next model of Ice Harriers have been delivered to SHIELD in New Jersey. These are endless war machines, which create their own fuel and armaments. They don't have the limiters which were supposed to keep the MK1's under control. And the remote detonation doesn't seem to work. And SHIELD won't listen to Natasha.
Cap decides they must go tackle the other Harriers themselves. CM questions the wisdom of invading a SHIELD base. BW wonders why the Harriers here went berserk. Thor gets fed up with all the talk, and flies off to deal with the problem alone. CM says the quinjet can't fly that fast, but she takes them it on a punishing sub-orbital arc to catch up.
Thor has gone ahead because he realises that the Ice Harriers went mad because they sensed him nearby, the killer of their parent. So now, as he approaches the New Jersey site, the new lot break their bonds too. (Not exactly the cleverest decision by the Thunder God.) And this lot seem to be able to cause him some damage.
As Thor is downed, the rest of the Avengers arrive. CM goes high to get a tactical overview, while IM goes in shooting and sowing anti-missile bomblets. Until a combination of lucky shots cripple his armour. BW uses the quinjet as a weapon, smashing into the creatures and frying them in its exhaust. Then she drops Cap, Hawkeye and Wolverine off.
CM swoops down to take out some of the Ice Harriers, and rescue the falling IM. She holds him up in the air so he can shoot at the enemy. Meanwhile Wolverine's adamantiun claws are slashing some of the ones on the ground to pieces. Armed SHIELD troops arrive as Cap and Hawkeye find the staggered Thor. They see the Avengers as the enemy, so Hawkeye holds them off.
There seems to be just one Ice Harrier left, and it goes after Clint. But Cap throws his shield up in the air, and Thor hurls Mjolnir to hit it and propel it through the Harrier's head.
The quinjet limps home, Thor carrying Tony's disabled armour. Following on from the idea that the Ice Harriers are driven mad by the presence of Thor, Wolverine wonders if the Nazi AI parts are also triggered by Cap. So if those 2 stay away, the Harriers will remain obedient.
Stark points out that primitive AIs like that would probably react to Logan, as another Super-Soldier. And (not quite so logically) that they'd target any super-powered being. (He jokingly excludes Hawkeye who has no super-powers. But then that also ought to apply to Stark himself.) Natasha thinks that may be exactly why SHIELD wanted the Harriers, as a counter to the super-population.
Talking of SHIELD, just then some of their flying craft appear and (literally) drop Bruce Banner off. He says SHIELD has been monitoring him for Hulk cells and they figure he's about due to transform. So they've brought him here as a sort of live bomb. He recites a speech they gave him, that the Avengers should promise to stand down before he Hulks-out. And that SHIELD will use the Ice Harriers as a defence system for when the Avengers mess up.
Cap and IM explain how the creatures can't be controlled. And that the Avengers intend to shut down the manufacturing site on Skrekklandet. Banner then reveals that he's plastered his chest with stress-reducing patches, so the Hulk won't appear for a couple of hours. He suggest sthe Avengers take him with them.
Everybody gets ready (renewing weaponry and clothing, and in IM's case new armour) and then they're off in a new quinjet. Against some other advice, Cap and Thor are going in 1st to talk the human inhabitants into leaving the Hereward facility before the Avengers destroy it. And also to see exactly what the situation is. But the base opens fire on the quinjet. Captain Marvel and Iron Man deal with the weapons, while Thor ferries Cap to the ground.
Inside the base (on the edge of the original crater) Thor and Cap find 2 people who claim to be descendants of 2 RAF guys who were in the plane with Cap in 1944. Hereward is a family business. However it turns out these 2 beings are really descendants of Nidhogg, and loads more come out of the walls.
Just then Hulk drops in and mops the floor with them. But even more Nidhoggs take their place. CM and IM are also on the ground fighting more of them. IM's armour has been damaged by a blast again, and once again he can only shoot, not move. Then BW, Hawkeye and Wolverine join in.
Inside the building Thor realises that they need to get to the source of the Nidhoggs, which will be underground. He starts to smash his way through the floor, while Hulk leaps into the original crater. On the way down Cap and Thor meet Wolverine. He had gotten IM to use thermal imaging to find warm bodies. He had then tracked down the 2 semi-human Nidhogg bosses, who were trying to escape. He killed them.
Outside BW has told IM to leave the fighting to the others and use his brain to find a solution to the problem. Tony reasons that the original Nazi AIs would communicate by radio, and that any sane creator would build in an off-switch. So he finds the radio command that turns all the little Nidhoggs off.
Hulk finds the big (original?) Nidhogg that is giving birth to all the new ones. When CM arrives down in the crater later she finds Banner, who says Hulk killed it. (But it had wanted to die. to end its existence as a living weapon. Irony, what!)
Thor stays on the island to call the lightning down again, to bury everything. The other Avengers return to New York by quinjet. On the way Cap tells Clint he's glad its finally over. Hawkeye retorts that war is never over. They've destroyed some weapons, but SHIELD and others will just build other kinds.