Mallory is almost embarrassed to admit it, but she doesn’t want the school year to end. She starts off each class by reading a poem and asking the kids to react to it. She chooses Nikki Giovanni, Gwendolyn Brooks, William Carlos Williams, Audre Lorde, Linda Pastan, Eldridge Cleaver, Robert Bly, and everyone’s absolute favorite, Langston Hughes. Mallory photocopies short stories by Joyce Carol Oates, Maxine Hong Kingston, John Updike. They discuss editorials in the New York Times. They read The Member of the Wedding by Carson McCullers, which only a few of the kids warm to, and then they read The Handmaid’s Tale, which is a crowd favorite. Dystopia, Mallory thinks. Teenagers love dystopia, the world as they know it falling apart at the seams. Her students keep journals in which they relate passages of what they’ve read to their own lives. They write short stories, sonnets, personal essays, persuasive essays, haiku (which they like because they’re short), and one research paper, mandated by the state, which makes the kids stressed and peevish, and the unit falls in the middle of March, when everyone on Nantucket hates everyone else anyway.

Mallory is popular because she’s young, because she’s “cool,” because she wears long blazers and leggings and friendship bracelets that the ninth-grade girls weave for her, because she’s friends with Apple (“Miss Davis”), who is also young and cool, because she talks to her students like they’re people, because she takes an interest in their lives. She knows who just started dating whom and who just broke up. She knows to pack an extra sandwich and invite Maggie Sohn, whose parents are divorcing, to spend lunch in her classroom so they can talk. She knows where the parties are, who goes, who doesn’t, who throws up, who hooks up. Some of this she gleans from reading the kids’ journals; some she overhears as they’re coming in and out of her classroom; some she hears from the kids who confide in her. Mallory locks it all in the vault, and opens the vault for Apple only—she never says a word to the principal, Dr. Major, to the parents, or even to JD.

And then, when it seems like things can’t get any better, they don’t. They get worse. Much worse.

Mallory was warned by Apple and the other teachers: Once the kids return from spring break, they’re impossible to control. And after the first seventy-degree day, forget about it.

Spring fever, Apple says. Everyone gets it.

Over April break, Mallory and JD go to Vieques, a tiny island off the coast of Puerto Rico. Mallory chooses it because it’s undiscovered, relatively undeveloped, and cheap. She books seven nights in a one-story beachfront motel in a tiny village called Esperanza. Their room is dim and the bedding iffy, but they aren’t picky. Mallory is cheered because the motel sits on a strip of white-sand beach on a turquoise bay. JD is cheered because the motel has a happening bar and restaurant out front.

On the first full day, JD plants himself on a barstool and starts drinking Modelos; after lunch, he switches to margaritas. Mallory is indulgent at first—she knows that JD is used to all-inclusive resorts where the point is to drink as much as possible in order to get your money’s worth, but after two days, she loses patience and begins to worry about their bill, which they’ve agreed to split. Mallory wants to explore the island. She wants to snorkel; she wants to tour Mosquito Bay and see the bioluminescence; she wants to visit the plaza in Isabel Segunda. There’s a nearby island called Culebra that has a famous Chinese restaurant. Mallory wants to hire someone to take them over by boat.

JD says, Sure, sure, whatever you want, baby. But getting him off his barstool is another matter. Mallory rents a mask and fins from the surf shop down the street and snorkels in the bay out front. She buys two tickets for the New Moon tour of Mosquito Bay, but JD is passed out cold at eight o’clock, so Mallory goes alone. It’s as she’s floating around and the water lights up around her—the dinoflagellates in the bay glow a brilliant blue when they come in contact with other creatures—that she finally acknowledges that she and JD just aren’t compatible.

They’ve been dating for eighteen months—though, as Mallory told Jake, it has been very casual. Or casual for Mallory, at least. JD is far more passionate about the relationship; he’s always asking for more. He likes Mallory to come watch him play darts at the Muse on Wednesday nights, which she does only when she doesn’t have too much grading. On Friday evenings after her standing happy-hour date with Apple, Mallory will join JD at the Anglers Club for their weekly appetizer party. This means clams casino and pigs in a blanket with a collection of longtime Nantucketers in the funky, weather-beaten clubhouse on Old South Wharf. JD invites Mallory to his parents’ house and introduces her as “my girl,” which makes her feel queasy. But it’s been nice, too, to have someone on the island day in and day out who cares about her. JD is in excellent physical condition but the sex is reminiscent of Mallory’s college years, with him humping and grunting in the dark; he’s intent on pleasing only himself. And JD is explosively jealous of every single man Mallory comes in contact with. He’s jealous of Dr. Major; he’s jealous of Mallory’s male students, especially the seniors.

Twice this past winter, JD mentioned moving in together, and the phrase nearly sent Mallory into shock. Moving in together can only mean JD moving into Mallory’s cottage—and no, sorry, that’s never going to happen. Mallory doesn’t even let JD do work around the cottage. Small jobs—fixing the bathroom fan, replacing the screen in the back door—Mallory has learned to do herself. Anything bigger—building the outdoor shower, having the cottage winterized, cleaning the chimney—she hires other people to do, and JD is jealous of all of them.

When Mallory gets back to the motel after the tour of Mosquito Bay and gazes upon JD snoring in bed, she decides to make a clean break once they’re back in Nantucket.

JD feels awful about missing the bioluminescence trip, so the next day, he arranges for a taxi to take them to Isabel Segunda. Once there, they wander the plaza holding hands and they stumble across a cute open-air bistro that is suffused with the heady scent of basil. Sure enough, the proprietress has just made pesto, which she tells them she’s going to drizzle over a tomato, peach, and fresh mozzarella salad. Yes, please, one for Mallory. JD orders the whole grilled fish. They sit at a table on the edge of a balcony overlooking the Caribbean. The proprietress fusses over them, calling them lovebirds, and two hours pass in such an enchanted way that Mallory wonders if she overreacted the night before.

JD pays for lunch and they wander out into the white-hot afternoon in a daze. They stroll a little more, poking into galleries and gift shops. JD wants to buy Mallory something, a souvenir that she can take home, and Mallory (tactlessly?) repeats her mother’s decree that anything one buys on vacation always looks like hell once you get it home. JD flinches. Has she ruined the mood? No, or at least not completely. He picks a red hibiscus blossom off a bush and tucks it behind Mallory’s ear. “Thank you for planning this trip,” he says. “I’m lucky to have you.”

They try to find a taxi back to Esperanza but have no luck. It’s hot, neither of them speaks much Spanish, and when they go back to the bistro to ask the proprietress for help, they find it shuttered, closed for the afternoon. JD starts to huff and puff. He prides himself on being a problem solver and doesn’t like feeling helpless. He flags down a white pickup and offers the driver twenty bucks to take them to Esperanza. The driver is a young, handsome Latino in a white polo. He smiles at Mallory—the flower in her hair—and accepts the money. Mallory and JD climb into the truck.