In Roald Dahl’s novel The Witches, what is the name of the potion that turns children into mice?

In Roald Dahl’s The Witches, Formula 86 Delayed-Action Mouse-Maker is the potion that transforms children into mice.

The Grand High Witch plans to distribute the potion through sweets sold in confectionery shops. Her scheme depends on timing: children who consume it do not change immediately, allowing the witches to affect large numbers of victims.

The unnamed narrator discovers the plan after overhearing the witches during their annual meeting. He is transformed into a mouse but works with his grandmother to fight back against the witches.

The title is sometimes confused with the 1990 film adaptation, which changes parts of the story and its ending. The potion’s full name is memorable because Dahl combines scientific-sounding wording with comic exaggeration.