The Secret of the Sword was a compliation of the first five She-ra episodes, explaining how Adora became She-ra.

The baby he stole was the Princess Adora. He bought her back to Etheria, and with the aid of Shadow-weaver's spells kept her ignorant of her true birth. So that Adam would feel no pain at the loss of his sister, the Sorceress removed any thoughts of his sister. The video begins with Adam being summoned by the Sorceress. She tells him to go to Etheria. She gives him a sword which looks just like his, but has a stone in it. He must find the owner of this sword. She opens portal for him, and he travels through it. He lands in Etheria, and bumps into Bow and Kowl. They take him to the Rebel Camp in the Whispering Woods and explain to him the history of Etheria. Some Horder Troopers arrive and Adam quickly transforms into He-man and fights them off. Hordak hears about this, and sets a trap for him. More TRooperas arrive, along with Force Captain Adora. While fighting her, He-Man notices that the stone in the sword is glowing. This distracts him and enables Adora to capture him.

The Rebels make a trip to Beast Island, in order to rescue He-Man. In the mean time Adora is talking to Adam, in his prison cell. He tries to persuade her that the Horde are evil, and that she should go out and see the truth for herself. The rebels are captured, except for Kowl, and he frees He-Man, and together they free the others. They flee back to the Whispering Woods. Adam decides he needs to talk to Adora so diguises himself as a Horde Trooper. Hordak captures him though, and wants to put him in the Maganbeam, which is Hordak's new toy. It will generate a laser beam, which Hordak plans to use to destroy the rebels, but he needs a person's power in order for it to work. Adam sees Adora and tries to talk to her again. Adora decides that she will go out and see Etheria.

She finds out that she has been lied to and confronts Hordak about it. But Shadow-Weaver sets a spell that makes her go to sleep and forget what she's seen. Hordak puts He-Man in the Magnabeam, which is slowly draining his power. In the same room are the two swords.

The Sorceress, through the stone in the sword calls to Adora, while she is sleeping. Adora wakes and goes to the room with the swords, where He-Man's power is being drained. The stone in the sword is glowing and through it the Sorceress speaks and tells her who she is, and that He-Man (Adam) is her brother. Adora knows that she must save He-Man's life, and lifts up her sword for the first time and says

"For the Honour of Grayskull,
I am She-ra"

She becomes She-ra and has the strength to save He-Man, just in time.

He-Man tells her to go and warn the rebels. She-ra runs to the stables to find her horse, Spirit, has become Swiftwind, a magical unicorn who cna talk. Together they fly to the Whispering woods and then She-ra goes back to get He-Man, who has destroyed the Magnabeam. At the Whispering Woods, the Sorceress again appears and explains things more thoroughly. The twins change back into Adora and Adam, and tell the rebellion about themselves. Glimmer explains that her mother, Queen Angella has been taken by the Harpies, and her Castle Brightmoon has been taken over by the Horde. She-Ra and He-Man save Queen Angella.

Adora and Adam return to Eternia so that she can meet her mother and father.

Hordak however has followed them into Eternia and with Skelator captures Adora again. Skelator tricks Hordak into returning to Etheria alone though. He-Man gathers a rescue party but She-ra manages to break free herself. They travel back to Etheria where they, with the help of the Rebels, free Castle Brightmoon.

Adam is returning to Eternia, but She-ra makes the decision to stay on Etheria until the Horde have been defeated. Adam says a tearful goodbye to his sister.