"Thor's hammer is missing again. The thunder god has a disturbing habit of misplacing his weapon--the mightiest force in the Nine Worlds. But this time the hammer isn't just lost, it has fallen into enemy hands. If Magnus Chase and his friends can't retrieve the hammer quickly, the mortal worlds will be defenseless against an onslaught of giants. Ragnarok will begin. The Nine Worlds will burn. Unfortunately, the only person who can broker a deal for...

Thor is imprisoned on the other side of the universe and finds himself in a race against time to get back to Asgard to stop Ragnarok, the destruction of his homeworld and the end of Asgardian civilization, at the hands of an all-powerful new threat, the ruthless Hela.