Margaret goes to Lincoln Center twice with her mother, but this isn't as much fun as her earlier Lincoln Center outing with her grandmother. She writes Sylvia a letter filling her in on aspects of her life, and Sylvia writes back, mentioning a man she has met in Florida, Mr. Binamin. She wants Margaret to come visit her over the spring vacation. Margaret writes back, saying that her parents will probably give her their permission, though it's too soon to make plans yet. Still, Margaret is extremely excited, having never been on a plane before. At the end of her letter, Margaret adds that two of her friends have gotten their periods already.
At the beginning of March, Nancy invites Margaret to spend the day in New York City with her family and with Moose, who has been Margaret's secret crush for some time now. They all go to Radio City Music Hall and then to the Steak Place for dinner. When Nancy and Margaret go to the bathroom, Nancy begins to cry and asks Margaret to go and get her mother, yet she won't tell Margaret what's wrong.
It is quickly revealed that Nancy is getting her period—however, it's her first time, and she lied before when she told Margaret and the other PTSes that she'd gotten it. Margaret feels angry, but Nancy begs her not to tell, and says she thought she had had it before but had made a mistake. Margaret finally agrees, though she still feels betrayed by Nancy's lie. At the end of the chapter, Margaret speaks to God about what has happened, declaring that she won't lie and that she'll wait for a heavenly sign that she's ready to grow up.
Margaret turns twelve on March eighth, and the first thing she does is use her mom's deodorant because she thinks that, as a twelve-year-old, she's going to start having an odor under her arms. Her mom laughs and says that Margaret can buy deodorant of her own. Sylvia sends Margaret a savings bond and three handmade sweaters, as well as a round-trip airline ticket to Florida. In school, the class sings happy birthday to Margaret, the PTSes buy her a record as a gift, and Nancy mails Margaret a separate card thanking her for being a good best friend, which makes Margaret suspect that Nancy is still afraid her small lie will be revealed.
Soon, Mr. Benedict assigns his class a group project to work on, and Margaret is put in a group with Laura Danker, Philip Leroy, and Norman Fishbein. Philip Leroy is rude, and Margaret decides that she doesn't like him anymore; this makes Margaret upset with everyone and by the end of this group of chapters she has begun to complain that her birthday was horrible.
The scene with Nancy in New York City is certainly the most dramatic and revealing event that occurs in these chapters, and says a lot about Nancy's character as well. Of all the girls, Nancy has always been the leader. She flaunts her knowledge of worldly subjects and been the PTS spokesperson, while the rest follow along willingly. But here, for the first time, Nancy shows her true vulnerability. She's so concerned with growing up, so concerned with being the first to experience new sensations and pass along her knowledge to her friends, that she feels like she has to lie in order to maintain her persona. It's hard not to sympathize with Nancy, despite her lie; she is simply far too eager to grow up, and she doesn't mean any harm.
Margaret's reaction to Nancy's lie is also quite important. Nancy was Margaret's very first friend in New Jersey, the first person in a new town to reach out and talk to her. Margaret has always thought very highly of Nancy and held her in a positive light, since Nancy helped integrate her into her new life. It's natural that Margaret feels betrayed by the knowledge that Nancy is perhaps not as infallible and wise as was once thought, and it's also natural that Margaret feels hurt that her best friend lied about something so important. But her willingness to keep Nancy's secret says a lot about Margaret's character; she's upset, but she won't let that stop her from being a good friend all the same.
Now that Margaret has had her birthday and turned another year older, she will undoubtedly be even more impatient to feel like she's growing up. Though she's technically no different from who she was immediately before she turned twelve, her new label makes her feel older. With age comes maturity, or so she hopes. But everything that frustrates Margaret—her friend's lie, her lack of growth, her missed period, and the fact that boys like Philip Leroy are actually quite rude and immature—is slowly building up. Though her birthday itself wasn't horrible by any means, Margaret has accumulated enough pent-up frustration to convince herself that it was.