Which Roald Dahl story was adapted into the 1990 film The Witches?

The 1990 film The Witches was adapted from Roald Dahl’s novel The Witches.

Dahl’s novel, first published in 1983, follows a boy who learns that real witches secretly operate across Britain. With help from his grandmother, he tries to stop the Grand High Witch’s plan to transform children into mice.

The 1990 film adaptation was directed by Nicolas Roeg and starred Anjelica Huston as the Grand High Witch. Although the film retains the novel’s central conflict, it changes some details and gives the story a different ending.

The book should not be confused with The Witches, a 2020 film adaptation of the same source material. Both films derive from Dahl’s novel, but the question identifies the earlier 1990 adaptation.