Shorts from "The New Adventures of Mighty Mouse and Heckle and Jeckle" Saturday morning cartoon show edited together into a movie. Space cat villain Harry the Heartless holds space mouse Queen Pureheart. Only Mighty Mouse can save her.

After experiencing traumatic nightmares of a time now past, the Sorceress summons Prince Adam and Cringer to Castle Grayskull to give Adam a precious, jeweled sword and send the pair to the planet Etheria to investigate its secrets.