Thor returns to Asgard, as he tries to restore order within the nine realms. His brother is locked away in prison for his crimes against humanity and the Asgardians. Meanwhile, a dark force emerges that forces Thor to forge an alliance with his brother, Loki, to combat a threat that could potentially destroy the balance of the universe as we may know it.

Tony Stark's life is falling apart at the seams. He's still haunted by the events of "The Avengers" psychologically. However, now it seems a mysterious threat known only as the Mandarin is out to make Tony's life a living hell. Now Tony must gather up whatever resources he has left to combat the biggest threat he's ever faced.