On the Planet Eternia, at the centre of the universe, the forces of Skeletor (Frank Langella) have managed to seize control over Castle Grayskull. Also, Skeletor has captured the Sorceress of Grayskull (Christina Pickles) who until now has kept order over the universe. Skeletor's is planning to recieve the powers of Grayskull when the 'great eye' opens and Eternia's moon is correctly aligned.
He-Man (Dolph Lundgren) who is also Skeletor's arch-enemy. During the fight He Man rescues a Thenorian named Gwildor (Billy Barty), who claims to be an inventor and locksmith. He Man and his comrades go to Gwildor's home where he reveals his newest invention; the "Cosmic Key", which can open a portal to any location and any time. He explains that Skeletor stole the key from him and used it to get into Castle Grayskull, but Gwildor kept the prototype. Gwildor uses his key to open a random gateway which He Man and his friends escape through. Their destination seems to be Earth, but on arriving there, the key gets misplaced and the Eternians split up to find it. Meanwhile nearby, a pair of teenagers named Julie (Courteney Cox) and Kevin (Robert Duncan McNeill) discover the key in a crater