Matilda turns her father’s pride in his appearance against him in a carefully prepared prank. After Mr. Wormwood dismisses her correct answer as cheating, she quietly substitutes platinum-blond peroxide for most of his hair lotion. The transformation is revealed at breakfast, where his alarm and his family’s reactions make the concealed act suddenly public.

Causes and Preparation

The prank follows an argument in which Mr. Wormwood refuses to believe Matilda has answered correctly. Though she is standing across the room from his paper, he accuses her of looking at what he wrote and calls her a cheat. His insistence that no one could simply know the answer, especially a girl, makes the accusation more than a dispute over one response: he treats Matilda’s ability as proof of dishonesty. The next evening, while eating tasteless fried fish and chips, Matilda ignores the television and considers her options. By bedtime, she has decided what to do. The narrative presents the prank as a considered reprisal, not a sudden accident.

The materials are already part of the household routine. Mrs. Wormwood’s hair is an intense platinum blond, refreshed every month between salon visits with a product labeled Hair Dye Platinum Blonde Extra Strong. Its label warns that it contains peroxide and should be kept out of children’s reach. Mr. Wormwood, meanwhile, has thick black hair parted in the middle and takes pride in keeping it glossy and firm. He repeatedly links strong hair to strong brains, a claim Matilda has answered by pointing out that Shakespeare was bald. Mr. Wormwood responded by telling her to keep quiet if she had nothing sensible to say. That exchange makes his appearance and his boast about intelligence part of the same target.

The Substitution

Early the next morning, Matilda locks herself in the bathroom. Her father’s routine gives her a precise opportunity: after shaving, he massages his scalp with Violet Hair Lotion, a strong-smelling purple liquid kept on the shelf above the sink beside the toothbrushes. His vigorous rubbing is accompanied by loud grunts and sighs, which Matilda can hear from her bedroom across the hall. The lotion is therefore familiar to her both as a bottle within reach and as a repeated, conspicuous ritual.

Matilda unscrews the cap and pours about three-quarters of the lotion down the drain. She replaces it with her mother’s platinum-blond peroxide product, deliberately leaving enough of the original lotion for the mixture to retain a reasonably purple appearance after she shakes it. She returns her father’s bottle to the shelf and puts her mother’s product back in the cabinet. The small detail of preserving the purple color shows the care behind the deception: the bottle looks familiar, and nothing in the bathroom is left obviously out of place.

Discovery at Breakfast

At breakfast, Matilda sits quietly eating cornflakes while her brother eats bread covered with peanut butter and strawberry jam. Their mother is in the kitchen preparing Mr. Wormwood’s usual meal: two fried eggs on toast, three sausages, three slices of fried bacon, and fried tomato. Matilda bends over her cereal and avoids looking up. She expects to see the result of her work but fears she will not be able to keep her composure if she does.

Mr. Wormwood enters noisily, as he characteristically does, and walks to the head of the table. When Mrs. Wormwood comes out carrying the loaded plate, she sees him, freezes, screams, and drops the food onto the floor. Her first alarm contrasts with her husband’s immediate concern about the mess on the carpet. She then points out his hair. Their son also cries out in astonishment, while Matilda says nothing and looks at the result with admiration. Her father’s formerly black hair has become a dirty silver, likened to a circus performer’s tights left unwashed for an entire season. The transformation is not the clean platinum shade of his wife’s hair but a visibly grimy, absurd version of it.

Aftermath and Significance

Mr. Wormwood reaches for his hair in disbelief and insists that he has not dyed it. His face turns pale green, like unripe apples, as he demands to know whether the family is playing a joke on him. The others can see what he cannot explain: the hair that he treats as evidence of his strength and self-regard has become a public embarrassment. Matilda’s silence lets the visible result answer the accusation without exposing how she produced it.

When Mr. Wormwood asks what he can do, Mrs. Wormwood advises him to have it dyed black, but first to wash it so that there will be something to dye. He immediately orders her to make an emergency appointment with her hairdresser, insisting that someone else can be moved down the list. He rushes upstairs to wash his hair while she sighs and begins calling the salon. The family’s ordinary morning has been overturned by a prank whose effects he must urgently try to undo. Matilda then remarks that he can do foolish things; her mother replies that men are not always as clever as they think. The ending links the physical humiliation to the earlier quarrel: Mr. Wormwood’s confidence in his own judgment has been challenged by a daughter whose planning he has underestimated.