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 the hammer`s return is the gods` worst enemy, Loki - and the price he wants is very high.