The film follows the plot of the 1974 book. The movie centers around Mildred Hubble, who is invariably the "Worst Witch" at Miss Cackle's Academy for Witches; a school of magic. Mildred creates many mishaps, including being late for school and making all of her classmates fall down, the incidents of when Mildred and her friend unintentionally turn themselves invisible, and transforming Ethel into a pig. The climax surrounds Miss Cackle's notorious twin evil sister, Agatha, plotting to take over the Academy. Ultimately Agatha is foiled by Mildred and Mildred establishes herself as the hero for the academy.