Young Heimdall sets out on a quest to save Odin - and everyone from Asgard.
It is a dark time for Asgard. The Allfather lies trapped in Odin's Sleep, which prompts the Frost Giants to attack directly. They evade the gods' defenses with unusual ease. Heimdall, a clever young warrior searching for his place among the defenders of Asgard, believes it is no coincidence that Odin is out of action and the giants are so well informed. He breaks into Odin's chambers and discovers that Mimir's severed head - a source of great wisdom - has disappeared. Accompanied by his sister, Lady Sif, Heimdall must search the Ten Realms to retrieve him so that Asgard does not fall.