Resolving to stop the Norse trickster Loki from invading Pinewood Bluffs with his army of monsters, Owen, Dana, Jon and Sydney stow away on Loki's sledge and find themselves in an underworld, where they face complicated challenges.
Fourth-grader Owen, whose everyday world is forever changed when he witnesses the disappearance of a classmate through the floor of their school, embarks on a daring rescue mission with friends Jon and Sydney.
Rescuing Dana from the underworld after making a dangerous pact with Hades, Owen, John, and Sydney tackle mythological Cyclopes who have taken over the power plant in Owen's hometown with the intention of building a monster army.