During a thunderstorm, a lightning hits Grim's scythe, transporting Billy to Asgard, land of the Norse gods. Then, Mandy and Grim go searching for him, while a viking wearing Billy's shirt remains at his house as a substitute. In Asgard, Billy learns about the endless battle in Valhalla, in which if a warrior dies, he is resurrected to continue fighting. In the end, Billy is surprisingly good at killing other Vikings, so Mandy and Grim are unable to convince him to return home.