When Eowulf, the pint-sized descendant of monster slayer Beowulf, decides to slay Cerberus, young Nico, Lula the sphinx, and Buck the unicorn must stop her or face the zombie apocalypse.

Zeus and his fellow gods-in-training face a new challenge in the underworld when they attempt to capture Cerberus, the three-headed guardian and cherished pet of Zeus's brother Hades. But they find themselves up against even more than they anticipated when they have to face off against Melinoe and her skeletal minions.