The narrator's parents are killed in a car accident during an icy Christmas visit to Norway.

Grandmamma becomes the narrator's sole caretaker and begins telling him about the dangerous world of real witches.

Grandmamma teaches the narrator the six signs of a real witch: gloves, wigs, blue spit, large nose-holes, toeless feet, and fire in their eyes.

Grandmamma honors the narrator's deceased parents' wishes and moves with him from Norway to England.

The narrator encounters a gloved woman near his treehouse and climbs to the very top to escape her.

Grandmamma falls ill with pneumonia, and the planned summer trip to Norway is replaced with a stay at Hotel Magnificent.

The witches shut and chain the ballroom doors, trapping the narrator behind the screen with hundreds of witches.

The Grand High Witch removes her beautiful mask to reveal an extremely hideous and shriveled face beneath.

The Grand High Witch reveals her plan to open sweetshops across England and poison all sweets with Formula 86 Mouse-Maker.

The Grand High Witch transforms a chocolate-obsessed hotel boy named Bruno Jenkins into a brown mouse before the assembled witches.

The witches smell the narrator behind the screen and the Grand High Witch forces an entire bottle of formula down his throat.

The narrator hatches a plan to steal the formula from the Grand High Witch's room and poison the witches' dinner.

The narrator uses his tail to swing above the witches' soup tureen in the kitchen and pour in the entire formula.

The witches eat their soup and transform into mice in the hotel dining room before all the other guests.

The narrator and Grandmamma return to Norway and make plans to track down and destroy witches across the entire world.

An unnamed boy loses his parents in a car accident and is raised by his witch-expert grandmother, Grandmamma, who teaches him everything about recognizing real witches. While training his pet mice in an English hotel ballroom, the boy accidentally stumbles into a secret gathering of England's witches and overhears the Grand High Witch's plan to poison children with Formula 86 Mouse-Maker. The witches discover and capture the narrator and force the formula down his throat, transforming him into a mouse. Working together as a team, the narrator and Grandmamma steal the formula, sneak it into the witches' dinner soup, and succeed in transforming every witch in the room into mice. With the witches of England defeated, the boy and Grandmamma return to Norway and begin plotting an ambitious global campaign to hunt down every remaining witch in the world.

The main plot from orphaned narrator to worldwide witch hunt.

The narrator explains that real witches look like ordinary women and blend into society, making them extraordinarily dangerous.

Grandmamma describes five Norwegian children who were transformed into animals or objects, or simply disappeared, because of witches.

Grandmamma declares that witches are not actually women at all but are demons that have taken human shape.

Grandmamma explains that the Grand High Witch rules all witches worldwide and summons them to a secret annual gathering.

Grandmamma gives the narrator two white mice named William and Mary as pets before the trip to Bournemouth.

Hotel manager Mr. Stringer objects to the mice in his hotel, but Grandmamma threatens to report his rat infestation.

Trapped in the locked ballroom, the narrator faints from fear but quickly recovers and peers through a crack in the screen.

An unnamed witch questions whether eliminating every child in England goes too far and is immediately incinerated by the Grand High Witch.

The Grand High Witch recites the bizarre and complex recipe for Formula 86 Delayed Action Mouse-Maker to the assembled witches.

The narrator's pet mice William and Mary escape into the meeting, and the Grand High Witch kicks them against the wall.

The narrator, now a mouse, convinces Bruno that he has transformed, and the two mice scamper back to Grandmamma's hotel room.

Grandmamma lowers the narrator inside a knitting sock from her hotel balcony down onto the Grand High Witch's balcony below.

The Grand High Witch unexpectedly returns to her hotel room while the narrator hides, frozen still, behind a bedpost.

The elderly witches arrive at room 454 to collect their formula bottles, and the narrator slips out through the open door.

Back in Norway, Grandmamma installs stepladders, a door-opening device, and a tiny toothbrush throughout the house to help the narrator.

The story opens with the narrator explaining what makes real witches so terrifying: they look like ordinary women, blend into society, and could be anyone. Grandmamma arms her grandson with vital knowledge about the children witches have harmed and the essential truth that witches are demons disguised in human form rather than actual women. During the hotel stay, small but consequential details like the narrator's pet mice and a tense standoff with the hotel manager set the stage for the chaos ahead. Inside the ballroom, the narrator witnesses the Grand High Witch incinerate a doubting witch, recite her bizarre recipe, and brutally kick the escaped pet mice across the room. The narrator's daring mission into the Grand High Witch's hotel room — lowered in a sock by Grandmamma, frozen in hiding as the witch returns, and slipping free when the elderly witches arrive — unfolds in tense, step-by-step detail. Finally, back in Norway, Grandmamma transforms their home into a mouse-friendly sanctuary, cementing her devotion and ingenuity.

Supporting details, key encounters, and behind-the-scenes moments.

Grandmamma corrects herself and admits that many witch victims did not vanish but were transformed into animals or objects.

Grandmamma reveals that a Secret Society of Witches exists in every country, all ultimately ruled by the Grand High Witch.

Grandmamma explains that England has fewer witches than Norway, but the English witches are arguably the cruelest on Earth.

The narrator spots that every single woman in the ballroom is wearing gloves and realizes with certainty they are all witches.

The Grand High Witch orders all the witches to quit their current jobs and purchase sweetshops across England.

The Grand High Witch provides ready-made formula bottles to the older witches who are too frail to gather ingredients themselves.

The narrator discovers that the Grand High Witch's room 454 sits directly below Grandmamma's room 554, with connecting balconies.

The narrator searches the Grand High Witch's room and finds the formula bottle hidden inside a torn-open mattress.

Grandmamma tries to warn Bruno's parents that their son has been turned into a mouse, but they refuse to believe her.

Mr. Jenkins shouts that he cannot have a mouse for a son and dismisses Grandmamma with insults.

A cook in the hotel kitchen spots the narrator and slices off part of his tail with a large knife.

Mr. Jenkins angrily confronts Grandmamma at her dining table moments before the witches drink their poisoned soup.

Grandmamma hands Bruno back to his parents on the way out of the dining room, causing his mother to scream.

The narrator learns that as a human-mouse he will live about nine years and rejoices that he and Grandmamma will die together.

Grandmamma reveals she impersonated a Norwegian police chief on the phone to obtain the Grand High Witch's real home address.

The story turns on a series of critical revelations, beginning with Grandmamma correcting herself about witch victims and then disclosing the secret worldwide network of witches governed by the Grand High Witch. Back in England, the narrator's dawning recognition that every woman in the ballroom wears gloves becomes the moment that exposes the entire genteel convention as a witch gathering. The Grand High Witch's decision to supply older witches with ready-made formulas reveals unexpected depth to the villain, while the narrator's discovery that her balcony lies directly below Grandmamma's unlocks the plan to defeat her. The aftermath reveals the worst of ordinary adults: Bruno's parents dismiss and insult Grandmamma, a kitchen cook violently injures the narrator, and Mr. Jenkins confronts Grandmamma at the dining table moments before the trap is sprung. The story closes on a hopeful note as the narrator embraces his mouse lifespan, celebrating that he and Grandmamma will die together, while Grandmamma reveals she has already tricked the police into exposing the Grand High Witch's secret castle.