As Asgard prepares the rebuild after Surtur's assault, on Earth, Loki has Igron prepare a mystical mask. Odin sends Thor to Earth to retrieve Loki.
There, Thor becomes Don Blake. Seeing Thor's arrival and transformation, Loki "rewards" Igron by transporting him to the dungeons of the trolls. Planning to ambush Blake at his office, Loki finds Thor waiting for him, springing a trap of his own. However, Loki unleashes the Living Mask on Thor and it exchanges their faces and powers. With his superior strength, Loki bests Thor, seizes Mjolnir, and trades clothing with him.
Although still recovering from his Sea of Eternal Night ordeal, Balder, sensing Thor's peril, rises from his sick bed and teleports to Earth with Sif. Finding Thor, they attack him, thinking he is Loki, while the real Loki watches from a distance, pleased. Defending himself, Thor uses Loki's power but, unused to it, nearly kills Balder. His genuine grief convinces Sif and the recovering Balder that he is not Loki.