Surveying the battle done by Surtur, Thor, and the Warriors Three encourages the warriors of Asgard to rebuild and repair the damage done. Later Thor meets with Sif, and the two have a brief romantic moment before Thor is greeted by Odin, who wishes the Thunder God to go to Earth and search for Loki.

As Odin transports Thor to Earth, Loki has shacked up in a posh penthouse using his magic tricks to make it appear that he is wealthy. He awaits Thor's arrival as his magician is preparing a special trap to use against the Thunder God. When he spies Thor arriving on Earth and resuming his mortal guise of Donald Blake, Loki drops his disguise and goes to Blake's office with his specially prepared trap.

Inside the office, Loki finds Thor waiting for him, and before the Thunder God can attack, he throws his latest creation: A living mask, which attaches itself to Thor's face. To Thor's horror, the living mask causes Loki and Thor to trade bodies. Now with Thor's matchless strength and appearance, Loki manages to knock Thor out and steal the Thunder God's uniform.

Back on Asgard, Balder has fully recovered from his ordeal of rescuing Odin from the Sea of Eternal Sleep. Not wishing to sit idle, he and Sif decide to go to Earth to help Thor capture Loki. They appear in Donald Blake's office to find what they think is Loki (but in reality, Thor in Loki's body) and attack. Thor tries vainly to convince them he is their friend trapped in their enemy's body. However, Balder and Sif refuse to believe it.

Meanwhile, the battle is being watched by Loki, who enjoys watching its outcome. As Balder and Sif are busy fighting the person they think is Loki, the real Loki in Thor's body decides to go about and ruin Thor's good name by rampaging across New York.

Finally, as the battle between Thor and Balder rages outside of Blake's office, Thor is forced to use Loki's magical powers against Balder. In his weakened state, Balder is knocked out, and Thor is mortified that he has possibly killed his best friend. When Sif arrives on the scene, she sees "Loki's" grief, and when Balder revives, the two are convinced that the person before them could not possibly be Loki, and the trio band together to find the real Loki and reverse the change that has been done to Thor.

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