A hooded man and his hired help make their way to a cavern in the icy north, which turns out to be a vault or a tomb of some kind as evidenced by the frozen frost giants. The guides either panic and run away or are killed and the stranger claims his prize: the Casket of Ancient Winters. Amora and Skurge show up to check on the man, revealed to be Malekith the Accursed, a dark elf who was, until recently, imprisoned in Niflheim. He turns on them and unleashes the full power of the Casket, covering the entire world in winter.
Meanwhile, it's a warm sunny day in New York. Hawkeye, Wasp and Hulk are enjoying the sun, so are reluctant to go assist Iron Man, Thor, and Black Panther who are caught up in a battle against Radioactive Man. After a brief skirmish, Radioactive Man begins draining power from the Arc Reactor in the Stark Industries building. Iron Man attempts to sink the reactor and Radioactive Man into the ground but Thor smashes the reactor's cooling pipes, opting to subdue him with large amounts of water instead. An argument breaks out when Thor starts ranting about the evils of mortal science but it has to be put on hold when snow starts falling over New York City. He recognizes the magic and explains the Casket's power. It turns out Odin hid the artifact on Earth long ago since it would be beneath the notice of most Asgardians.
Tony calls Thor out on how a magical artifact is causing just as much damage as human science, continuing the argument from before, and T'Challa deduces that the Casket is located in Norway, despite the fact that Stark was previously unable to determine any pattern in the magic's effects.
The situation gets progressively worse as ice monsters start emerging from the snow. The rest of the Avengers fight back against them with the help of the Fantastic Four while Iron Man heads to Norway with Thor and Panther to stop the problems at their source. Iron Man and Thor continue to trade snarks about magic and technology.
(the engines on the quinjet ice up)
Thor: Indeed we do have irony, just as you are having some right now.
Iron Man: I hate magic.
The trio confront Malekith, who promptly freezes Thor and announces his plan to turn Midgard into a new home for the dark elves. He then sics the hounds on Panther and Iron Man, and draws upon the power of the Casket to make himself unstoppable. Panther tells Iron Man and Thor in no uncertain terms that they will need to combine the strengths of magic and science if they hope to beat Malekith. Thor then hits Iron Man's armor with lightning, supercharging it, and allowing him to defeat the dark elf. With him out of the way, they are able to close the Casket and banishes all the spirits and ice monsters back where they came from. Iron Man and Thor manage to settle their differences but they are jumped by Amora and Skurge, who take the Casket. Thor attempts to return to Asgard and warn the other gods of the Enchantress' treachery but finds that the way is sealed. He can't go back.
Tropes:
- Badass Boast:Thor: You and your people were destroyed by the Frost Giants! How did you come here?!
Malekith: I walk in both worlds now, Odinson. The living... and the dead!
Thor: Then I shall send you back where you belong, Elf! - Battle Cry: "It's clobberin' time!"
- Berserk Button: Malekith becomes enraged over Black Panther managing to hurt him.Malekith: You dare?! A mortal thinks he can hurt Malekith the Accursed?! A mere man?!
- Big Bad Wannabe: Malekith intends to conquer Earth for himself and makes a pretty good attempt at it, but Amora notes he's nothing compared to The Man Behind the Man.
- Big Damn Heroes: As more ice monsters appear, the Human Torch and Thing arrive to lend Cap a hand.
- Bittersweet Ending: The world is safe from Malekith, but Amora and Skurge escape with the Casket, and Thor learns the hard way that he's been barred from Asgard.
- Both Sides Have a Point: Thor and Tony argue with each other about the callous use of science and magic. While Thor makes a statement against science by pointing out the science-based villains making up a majority of the threats the Avengers has faced, Tony rightfully brings up about Amora and Executioner, especially since they are now part of the Masters of Evil. In the end, they both realized science and magic can benefit one another.
- Call-Back: When stating his low opinion of magic, Iron Man cites Amora previous attacks on the team, as well as Skurge nearly killing him.
- Deadpan Snarker: Black Panther gets in his share of digs at both Iron Man and Thor.
- Dramatic Irony: Thor has no idea why he's been barred from returning to Asgard, but in an earlier scene, Loki was mentioned multiple times as being both Amora and Malekith's superior.
- Earth Is the Center of the Universe: Odin hid the Casket on Earth, though Thor suspects it was because most Asgardians never bother with the planet in the first place.
- Fake Ultimate Hero: Played for laughs after Malekith is defeated. When Hawkeye and Hulk come to and ask what happened, Wasp jokingly insists she saved the day.
- Fanservice: Jan and Clint in swimsuits.
- Foreshadowing: Before departing, Amora assures Thor, "It will all be over soon."
- Greater-Scope Villain: Loki is formally revealed to be this, being the one giving Amora her marching orders and reviving Malekith to retrieve the Casket.
- Harmless Freezing: Happens to Hulk and Hawkeye.
- Headbutting Heroes: Iron Man and Thor spend the episode sniping at each other, due to their longstanding different attitudes on science and magic. The fight with Radioactive Man gets it going here and the crisis with the Casket just further inflames it. This is resolved when they work together to take down Malekith.
- Humans Are Insects: Thor believes the Casket was hidden on Earth precisely because Asgardians typically don't concern themselves with anyone or thing living on the planet, humans included. Malekith is later openly enraged when Black Panther manages to score a good hit, feeling that "a mere man" had no right to do so to him.
- Irony: As noted in the above quote.
- Lampshade Hanging:
- When Iron Man asks if he's doing all right against Radioactive Man, Black Panther says his suit was designed to withstand radiation. An indignant Iron Man remarks he should've seen that one coming by now.
- Malekith observes there's very little iron in the armor belonging to a guy calling himself Iron Man.
- Little "No": Amora when she realizes that Malekith is going to use the Casket on her and Skurge.
- The Man Behind the Man: According to Amora, it was Loki who revived Malekith and tasked him with retrieving the Casket.
- My Significance Sense Is Tingling: While berating Iron Man, Thor suddenly gets a headache. He's sensed the opening of the Casket.
- Mythology Gag: Hawkeye says they should move to the West Coast. In the comics Hawkeye founded and led The West Coast Avengers.
- Oh, Crap!: Thor when he realizes he's been locked out of Asgard.
- "Oh, Crap!" Smile: Hawkeye after Hulk complains about being left in a frozen pool.
- Only Sane Man: Black Panther gets Iron Man and Thor to stop their petty bickering.
- Properly Paranoid:
- Amora was sent to check up on Malekith's progress, making it clear that no one trust him. Malekith demonstrates they were all right to question his loyalties.
- Thor immediately suspects that Amora was working with Malekith.
- Something We Forgot: Before encountering Malekith, Thor spots Amora frozen in ice. In the last scene, as the group celebrates their victory, they're suddenly restrained by Amora's magic. Iron Man lampshades how they forgot about her.
- The Starscream: The main plot kicks into gear because Malekith is this. After making his move, Malekith remarks that Loki and Amora were right to distrust him. Amora also suggests that even Malekith's own people knew he was this and never trusted him.
- Tempting Fate: Iron Man goading Thor about irony really comes back to bite him.
- Title Sequence Replacement: Disney XD aired this episode after a break that lasted several months, so they attached a Previously on… segment to the beginning, and replaced the theme song with a 30-second expository speech. All the other versions of this episode play without the recap, and have the theme song in place of the speech. This would also happen to the six following episodes.
- Two-Faced: Malekith.
- Wham Episode: Though hinted at previously, Loki is formally revealed to be the season's Greater-Scope Villain. Thor is also barred from returning to Asgard.
- Wham Line: "It is as if Loki does not trust me."
- Wham Shot: The portal to Asgard blasting Thor away.
- What the Hell, Hero?: Played for laughs when Hulk catches up with Hawkeye and Wasp.Hulk: You left Hulk in the pool! IT FROZE!
