Magnus Chase and the Hammer of Thor is the second book in Rick Riordan's Norse mythology series, in which Magnus and his friends must retrieve Thor's missing hammer, Mjölnir, to prevent an onslaught of giants and stop Ragnarok. Plot Summary The story begins six weeks after the events of the first book, The Sword of Summer. Thor's hammer, Mjölnir, has gone missing again, but this time it has fallen into enemy hands, leaving the Nine Worlds vulnerable to a giant invasion. The Quest Begins: Magnus Chase meets Otis, one of Thor's goats who is acting as an informant, for a lead on the hammer's location. Before Otis can reveal much, he is killed by a wolf-masked assassin (who is actually Utgard-Loki, king of the frost giants). The only clue is a cryptic warning to stay away from Provincetown. Magnus, along with his friends Samirah al-Abbas (a Valkyrie and daughter of Loki), Blitzen (a dwarf fashion expert), and Hearthstone (a deaf elf rune magician), realize the urgent need to find the hammer. Loki's Plan: They soon learn that the giants have the hammer, and the only person who can broker its return is the manipulative god Loki, who is currently bound in a cave. Loki demands a high price: Samirah must marry the giant Thrym to retrieve the hammer as part of a traditional wedding gift exchange. This would also allow Loki to receive the mythical Skofnung Sword from the "father of the bride" (Loki himself), which can cut his bonds and free him. New Allies and Trials: The group travels to Alfheim so Hearthstone can confront his past and acquire the Skofnung Stone, the only item that can heal a wound from the Skofnung Sword (which is needed to save the petrified Blitzen after an encounter with a wight). They are also joined by a new einherji, Alex Fierro, another one of Loki's children who is genderfluid and a talented shapeshifter. The Wedding and Escape: To keep Samirah from a forced marriage and uphold her vows to her mortal fiancé Amir, Alex volunteers to pose as the bride, using their shapeshifting abilities to trick Thrym. At the wedding, Alex reveals their true identity and attacks Thrym, causing chaos. In the melee, Loki manipulates Magnus's uncle, Randolph Chase, into using the Skofnung Sword to cut his bonds. Despite the arrival of Thor and other gods, Loki escapes his imprisonment, and Randolph is killed by the sword's spirits. Aftermath: Thor retrieves Mjölnir and the giants are defeated, but the victory is bittersweet as Loki is now free and planning to sail the ship Naglfar to begin Ragnarok at Midsummer. Helgi, the manager of Hotel Valhalla, assigns Magnus and his friends the mission to find and recapture Loki. To prepare for the new quest, Magnus decides to seek help from his cousin Annabeth Chase and her boyfriend, Percy Jackson.