Prince Orwall is delivering supplies to the Great Rebellion, risking Horde scrutiny, but Adora is very grateful for his assistance. Catra and an army of Horde Troopers ambush them, but Adora ensures that the Prince takes Spirit and rides to safety. She transforms into She-Ra and destroys the Horde Troopers. Catra uses a new weapon to pick up nearby boulders and change them into a cage, but before she is able to use it, She-Ra falls down a hole in the ground, and Catra follows her in pursuit. She-Ra finds herself in a maze of underground corridors.
As Catra follows, she notes the strange underground buildings with their cat imagery, and subsequently stumbles into a city of cat people. Catra assumes her feline form after she hears two inhabitants, Tao and Percival, talking about their missing Queen. When Catra presents herself, they mistake her for their Queen. Catra plays dumb so that she can listen to them as they tell her of their history: When the Horde arrived on Etheria, they took some of the cat people as their slaves, which compelled their Queen to leave to rescue her people as the other cats fled into the underground. The Queen wore the same mask from which Catra gains her power. At that moment Catra realizes that Hordak must have captured the real Queen and given her the mask shortly thereafter. After using the mask's freeze-fire abilities, she earns the allegiance of the cat people, as she plans to exploit that loyalty by ruling her new empire.
She-Ra stumbles upon the city at that moment, and the "Queen" orders that She-Ra be captured. She is the only possible spoiler of her deception, so Catra resolves that she must never escape the city. She-Ra befriends Percival and tells him about Catra's employment in the Horde and her deception. She reveals to Percival that while she once worked for the Horde, she learned that the real Queen had become a Horde slave. Percival is compelled to investigate, and when he spies on Catra, he sees her communicating with Hordak, confirming the authenticity of She-Ra's account. He frees She-Ra, and they rush to prevent Catra from assuming the throne once more in the crowning ceremony. She-Ra charges that Catra is an imposter to the throne, prompting Catra to spring an attack on her. Catra uses the throne's weapons to attack her, but She-Ra dodges the blasts, deftly unmasking Catra and revealing her human form.
She-Ra chases her out of the underground kingdom, and Percival and Tao assure her that Catra will remember none of what she has seen. The power of the Magicats is the power of illusion, and the power of the kingdom is that outsiders can be forced to forget its existence. She-Ra helps the cat people recover their Queen, by having Percival impersonate Hordak using the communicator, which Catra dropped in her hasty exit. Per "Hordak's" instructions, the Queen is released and brought to them. Grateful for She-Ra's help, the Magicats agree to use their power of illusion to help Prince Orwall deliver the rebel supplies under a cloak of invisibility.
Synopsis by Michael Cravens