As Matilda eats her “awful” fish and chips, she decides how to punish Mr. Wormwood. The next morning, Matilda gets up early and goes to the bathroom. Mrs. Wormwood gets her mousy brown hair dyed blonde at a salon every six months, but she touches up her roots often at home with a product called “PLATINUM BLONDE HAIR-DYE EXTRA STRONG,” which has a warning label about the peroxide content. Mr. Wormwood has lush black hair, which he keeps that way by rubbing a hair tonic into it every morning. (As he does this, he emits “masculine grunts.”) Matilda tips most of Mr. Wormwood’s hair tonic down the drain and fills the bottle up with her mother’s dye.
The fact that the narrator continues to bring up that Mrs. Wormwood isn’t a natural blonde is an indicator that Mrs. Wormwood is failing to embody a feminine ideal. She’s blonde and busty, but readers are supposed to see this as an unsuccessful ruse. Mr. Wormwood, on the other hand, is trying hard to make himself seem as big, important, and masculine as possible, as evidenced by his “masculine grunts” as he attends to his hair. Dyeing his hair blonde will deprive Mr. Wormwood of his prized hair, something he sees as a symbol of his masculinity and success.
Later, Matilda and Michael are eating breakfast in the dining room while Mrs. Wormwood busily cooks up Mr. Wormwood’s breakfast. Mr. Wormwood bustles into the room, purposefully being loud to alert everyone that “the master of the house, the wage-earner” is here, and slaps Michael on the back. Matilda studies her cornflakes—she doesn’t want to laugh if she’s been successful. Just then, Mrs. Wormwood comes into the dining room with her husband’s breakfast, and she screams and drops the plate. Mr. Wormwood scolds her for making a mess.
Referring to Mr. Wormwood as “the wage-earner” implies that Mrs. Wormwood doesn’t have a job; her job is to be a housewife and care for her husband and children. So keep in mind that her livelihood depends on Mr. Wormwood’s inherently unreliable shady business practices. Mr. Wormwood also asserts his power here when he scolds Mrs. Wormwood for dropping the plate and making a mess—this implies that it’s his house she lives in, and she’s messing up his house.
In a shriek, Mrs. Wormwood asks what Mr. Wormwood did to his hair. Michael joins in and shouts too; Matilda stays silent. Mr. Wormwood insists he doesn’t know what everyone is talking about until Michael notes that his father’s hair is “the same colour as mum’s only much dirtier looking.” At this, Mr. Wormwood shrieks for a mirror. Mrs. Wormwood offers him her powder compact, which contains her best Elizabeth Arden powder. He spills the powder on his chest and then shouts when he sees his reflection. Matilda offers that he must’ve mistakenly used Mrs. Wormwood’s bottle of hair product instead of his own.
Unexpectedly (and certainly not on purpose), Michael helps Matilda torture their parents when he insultingly describes Mr. Wormwood’s new hair color as “dirtier looking” than Mrs. Wormwood’s. Spilling Mrs. Wormwood’s best powder as he hurries to look at himself also shows how little Mr. Wormwood actually cares about his wife; it doesn’t seem to occur to him that he could respect his wife’s belongings. This may also reflect how precarious Mrs. Wormwood’s security really is.
Mrs. Wormwood agrees that this is probably what happened. She notes that she’s only supposed to use a tiny bit and dilute it—Mr. Wormwood might lose his hair after using so much. Peroxide, after all, is what they clean lavatories with. Matilda suggests her father wash his hair well. As he runs to shampoo his hair, Mr. Wormwood commands his wife to make him an emergency appointment to get his hair dyed back. Alone with her mother, Matilda observes that Mr. Wormwood does silly things. Mrs. Wormwood responds that men aren’t as smart as they think they are.
On the other hand, Mrs. Wormwood doesn’t seem to think very much of her husband—she doesn’t seem to think he’s particularly intelligent, given what she says here. This is another potential indicator that the Wormwoods’ marriage isn’t especially strong, which could jeopardize Mrs. Wormwood’s security. But Mr. Wormwood seems to totally ignore or overlook all of this, since he gets what he wants when he orders his wife to make him an appointment.