When the book opens, the narrator—a boy whose name is never given—provides basic information about witches, such as their focus on harming children, their methods, and their global distribution. They are always female, and they cannot be identified simply by their appearance. Even one’s own teacher, he says, might secretly be a witch.
The boy tells the reader that he has twice escaped from witches. Both events happened before he was eight years old, and he has his wonderful grandmother to thank for being alive to tell the truth about those encounters. Currently the young boy and his grandmother are living in Norway. Until he was seven he had lived in England, but during a winter family visit, his parents were killed in an automobile accident. Since their death, he has lived with Grandmamma, whom he adores.
Grandmamma knows a great deal about witches, including their taking children or turning them into animals. She wants to keep her grandson safe. While in most ways witches resemble human women, they do have a few features by which he can recognize them: bald heads (usually covered by wigs), claw-like hands (on which they wear gloves), toeless feet, and blue, ink-like spit. Her willingness to discuss them has limits, however; she will not say why she is missing a thumb.
As his parents had wished, the boy and his grandmother go to live in England. Grandmamma tells the boy that English witches tend to favor the use of potions that can turn children into slugs or bugs. Their parents, not recognizing them, might kill their own children. Most dangerous and cunning of all is the Grand High Witch of the World, whom the others visit annually. Grandmamma identifies as one of the “witchophiles” who try to learn more about them, such as where their meetings take place.
After the boy’s school term ends, they plan to take a holiday in Norway. Before the trip, however, the grandmother develops pneumonia. Rather than travel to Norway, her doctor suggests she recuperate further in coastal England. At their hotel in Bournemouth, the boy gets into some trouble when his new pet mice alarm the maid.
The boy stumbles onto a meeting of the Royal Society for the Prevention of Cruelty to Children. Secretly observing one of the attendees scratching her bald head under her wig, the boy determines that this is the witches’ society. When one apparently young, lovely woman removes her mask, he realizes that the real, shrunken, shriveled face beneath is that of the Grand High Witch.
She declares that their mission is to kill every child in England. They will do this through a network of sweet shops, from which they will sell candy tainted with "Formula 86 Delayed Action Mouse-Maker." Within a day of eating the candy, the children will turn into mice, and the adults will trap and kill them. As they agree to the plan, the witches sing a scary song about the children’s demise. They next review the composition of the formula, which includes ordinary ingredients such as mouse tails, but also components from exotic animals such as the gruntle, blabbersnitch, and grobblesquirt.
To test Formula 86, they give tainted candy to a boy named Bruno, who comes to the meeting room for candy. The narrator, still hidden, recognizes Bruno as a rich boy he met who liked to eat and complain. After eating the sweets, Bruno quickly turns into a mouse, but he escapes. The Grand High Witch changes the plan; instead of concocting the formula themselves, the other witches can get pre-mixed bottles, which she has in her hotel room.
The witches detect the boy’s scent, which they identify as dogs’ droppings. With the doors locked, he cannot escape. They capture him and pour Formula 86 down his throat. Feeling a burning sensation, the boy shrinks and grows fur, and his hands turn into paws. Before they can catch him, he scampers off and hides. Unconcerned, the witches leave.
When the boy encounters Bruno, they are both surprised that they can still speak in their human...
(The entire section is 1,224 words.)