Percy is given the task of locating Zeus's original lightning bolt before an all-out war can break out between the gods. He chooses Annabeth and Grover to accompany him to the realm of Hades, as Hades is the most likely culprit of the theft. Before he leaves, Percy is given Chiron's magic sword "Anaklusmos" ("Riptide") and Luke's flying sneakers. The trio travels towards Los Angeles, where the entrance to Hades's realm resides. Along the way, they are attacked by several monsters, including the Furies, Medusa, Echidna, and the Chimera. They also do a favor for the god Ares, who gives them a backpack full of supplies and safe transportation to Nevada. Percy gradually learns more about his companions, his powers, and the world of the Greek gods. When they arrive in Hades's realm, Grover is nearly dragged into Tartarus by Luke's flying shoes. The battered group finally meets Hades, who reveals that his Helm of Darkness has also been mysteriously stolen, and accuses Percy of stealing it. Hades threatens to kill Sally Jackson (who is being held hostage by the god) and reanimate the dead unless his helm is returned. When Percy finds the missing master bolt inside Ares's backpack, the group realizes they've all been manipulated by Ares. Narrowly escaping the Underworld, Percy challenges Ares to a duel on the beach. After a long and tough fight, Percy wins, and he gives the Helm of Darkness to the Furies. Hades realizes that Percy is not the thief of the helm nor the master bolt, and returns Mrs. Jackson to their apartment in New York.