As Baron Dark continues to invade villages and enslave humans in his weapons factory, the Legion of Light decides that one of their own has to shut down the factory from inside. Guardian volunteers for the dangerous task and goes undercover. But before he does he finishes developing a weapon of his own: one designed to destroy a Skeleton Warrior’s Heartstone in order to turn them back into humans.

Grimskull and Guardian plan to destroy Baron Dark’s new battleship, The Gorgon. Talyn and Prince Lightstar go to the Semigon kingdom to warn them of Baron Dark’s imposing threat, but are confronted by Dagger and Shriek and are thrown in prison. Lightstar, however, is able to turn Dagger and Shriek back into humans and make them confess Baron Dark’s new plot.