A villain from Red Hulk's past takes out the Agents of S.M.A.S.H. one-by-one to exact revenge and frame the team for destroying Vista Verde.

Skaar accidentally triggers Ragnarok and incites the ire of Asgard. Detained by the all-seeing, all-knowing guardian of the Bifrost, Heimdall, the Hulks must save Skaar and battle Thor. Soon the Heroes find they must put aside their differences to fight against Malekith and save the realm.