Magnus Chase is a homeless boy in Boston. He is awoken by his friend Blitzen, who tells him that two people are looking for him. Magnus wonders if it is police looking to question him about his mother's murder 2 years ago.
Magnus breaks into his Uncle Randolph's mansion. There he finds his Uncle, who tells him he has to retreive his birthright from a river, where his father lost it about 1000 years ago. Magnus is confused and thinks his Uncle is crazy.
When they arrive at the Longfellow Bridge, Magnus is confronted by Surt, a fire giant. Magnus retrieves his birthright, a sword, and tries to kill Surt, to protect the mortals on the bridge, and Magnus ends up dying, but he takes Surt with him into the water when Surt pushes him.
Magnus wakes up in the Hotel Valhalla, a Norse afterlife for the warriors of the dead. He meets his Valkyrie, a girl named Samirah, who tells him he is dead and that she brought his here. He gets is own room with exactly what he would want.