Young Kevin, the crown Prince of his father's realm, is studying the boring laws of his kingdom in preparation for his adult responsibilities. When his farther leaves the room Kevin decides to run away and play instead.
Meanwhile, Adora and Bow wait to meet Madame Razz, planning to go to the Twigget Carnival. Flutterina appears and decides to accompany them.
At the Fright Zone, Shadow Weaver advises Hordak to use a spy to infiltrate the Twigget Carnival and carefully watch the rebels' every move. Realizing that he has dispatched all of his Spybots to Horde World, Hordak orders Mantenna to open a dimensional gate to bring them back. However, the dimensional gate goes awry, opening on Kevin's world, Kevin accidentally flying through it. Shadow Weaver sees potential in Kevin, and uses her magic to enchant him to do the bidding of the Horde as a spy. She presents Kevin with an opportunity to save Flutterina from a giant spider, thus earning her trust and allowing him to penetrate into the ranks of the Rebellion.
Flutterina is grateful for his help, but because he has trouble with his memory, she invites him to attend the carnival to ask the rebels for help. Flutterina arrives at the carnival and introduces the rebels to Kevin. At that moment, Kevin excuses himself and goes to find privacy, where he can burst a capsule, which creates a black cloud to serve as cover for a Horde attack, prompting Adora to transform into She-Ra. As Bow and the Twiggets use buckets of water to short-circuit the Horde Troopers, Hordak traps Flutterina in a net. Kevin stands helpless in Shadow Weaver's thrall. She-Ra uses the Sword of Protection as a magnet to destroy the Horde Troopers, but the Horde soon flee with Flutterina. Kowl tells the others that Kevin was responsible for the black cloud, She-Ra and Madame Razz connecting the dots to realize that Kevin must be under a powerful spell.
Madame Razz consults her magic mirror and discovers that Flutterina has secretly been sent to Horror Hall in an attempt to trick the rebels. She-Ra defeats Hordak's ship on its journey back to Fright Zone, defeating Hordak and Mantenna. She-Ra and Kevin fly ahead to Horror Hall to free Flutterina. There, they face Shadow Weaver and Leech, and soon see that the spell controlling Kevin is powerful, as Shadow Weaver regains control of the young boy. Shadow Weaver uses a magic rope to drain She-Ra and Swift Wind's strength, as Kevin struggles to break free from Shadow Weaver's spell.
Kevin is ultimately able to overcome the spell with the pure power of good. As She-Ra breaks free of the rope, Kevin picks up Flutterina on his ship and they all escape from Horror Hall. Kevin's father arrives to collect his son, Kevin having learnt a lesson in love.
Synopsis by Michael Cravens