Eternia is being invaded by the Horde army, led by Hordak, through a star gate. The heroes try to disable the gate, but during the battle it becomes an unstable gravity-dense vortex.
He-Man and Hordak are sucked through it and end up on Aarboria, a planet once under Horde control, both with a case of amnesia. As they stroll through town, people yell insults at Hordak and slam their doors to him.
Both are confused as to why they are being treated this way. Suddenly, a planet-quake occurs. While He-Man holds up the arena pillars, Hordak saves a young boy who had fallen into a crevice. Prince Bar'in arrives with some knights and orders that they be made to fight a two-headed serpent for their lives in the arena, despite their heroics, as they are suspected of both being Hordesmen.
Hordak defeats the monster and frees He-Man, but Bar'in goes back on his word and orders his guards to sieze them. Just as they surround them, an Eternian ship lands with Man-At-Arms and crew onboard, ready to take He-Man home. A Horde ship also arrives, and Shadow Weaver restores Hordak's memory against his will. He-Man, after regaining his memory, invites Hordak to join them, but Hordak replies that he is simply too old and set in his ways to change now.
Flying away, Shadow Weaver says that it is their opportunity to destroy the heroes' ship, but Hordak intentionally misses them.
Interesting trivia: The planet Aarboria is a not so subtle homage to the kingdom of Arboria from Flash Gordon comics and assorted media. Likewise is Prince Bar'in a homage to Barin, prince of Arboria and close friend of Flash Gordon.