Vivi peers into the formal living room to the right of the stairs and the dining room to the left, each room with a brick fireplace. Savannah leads her down the hall to a library, which is everything you’d want an at-home library to be. Built-in shelves hold rows and rows of books—the requisite leather-bound kind but also the rainbow spines of popular hardbacks and an entire swath of battered paperbacks. There’s a deep leather armchair where apparently someone has been sitting recently—a copy of Moby Dick lies splayed open on the seat. Vivi can’t help herself; she picks the book up. In the margins are notes in faded pencil.

“I was just revisiting Melville,” Mary Catherine says. “That’s the copy I studied from at Smith, if you can believe it.”

Vivi sets the book down with some reverence now. The library isn’t just for show; it’s the place where Mary Catherine can revisit Melville and reflect on the thoughts she had as a younger person. Vivi understands that she’s in a home where things aren’t put out for show; the furnishings have meaning, provenance. It’s mortifying to compare this home—Savannah’s second home—to the place Vivi grew up, with its wall-to-wall carpeting, crucifixes everywhere, the long, fancy mirror at the end of the hall bought on sale from the furniture department at Higbee’s.

Vivi wishes she hadn’t sold all her books back to the student bookstore at the end of the year. She, too, wrote in the margins (this was a detriment to their resale value) and now she will never be able to revisit her musings; she will never be able to hand off her copy of Franny and Zooey to one of her children and say, I read this at nineteen, let me know what you think.

From now on, she decides, she’s saving her books.

Beyond the library is a huge, wide, bright kitchen, which is many different rooms in one. In front of a row of windows is a harvest table set with ten Windsor chairs. Against the opposite wall is an enormous cast-iron range with an imposing hood; the backsplash tile is painted with pictures of fruits and vegetables labeled in French: haricot vert, artichaut, pêche. There’s a plaid Orvis dog bed in the corner and beyond that a mudroom where Bromley’s leashes hang alongside yellow rain slickers. A straw market basket rests on a simple wooden bench that is probably where good old Ollie Hamilton used to sit to put on his boots.

The kitchen has a square island topped in dark marble. There’s a prep sink at one end and three barstools at the other. Someone has set out a cutting board with a block of pale cheese, a stick of salami, and a dish of purplish olives.

“Alcohol?” Savannah asks. She pulls a bottle of wine from a fridge that seems to hold only wine, and Vivi can tell it’s not the cheap stuff that she and Savannah used to buy at Kroger and drink in the dorms before they went out.

Savannah takes two wine goblets down from a rack over their heads that Vivi hadn’t even noticed and says, “Let me show you upstairs.”

The hallway of the second floor is long, with a barrel-vaulted roof. Doors that lead to bedrooms—or bathrooms? or closets?—are all closed. At the end of the hall is a rounded niche holding the most impressive model ship Vivi has ever seen. This house is like a museum; there isn’t one cheap or inauthentic thing in it.

They ascend another set of stairs to the third floor, Savannah’s floor, the renovated attic. The massive, airy, slope-ceilinged space is entirely white—walls, trim, curtains, king canopy bed. The rag rug is done in vivid rainbow stripes, and hanging on the walls is Savannah’s childhood artwork—finger-paintings, crayon drawings.

It’s a “self-portrait”—Savannah with green hair and red pants drawn like two long boxes—that finally moves Vivi to tears. She brought home school projects—turkeys created by tracing her hand, Easter bunnies with cotton-ball tails, even a tessellation Vivi slaved over for her geometry class in ninth grade—and she’s certain they all went into the trash. Vivi’s family never documented or celebrated itself because neither of her parents believed their family was worth it. They were just trying to survive, and they didn’t even succeed at that.

“What’s wrong?” Savannah asks.

Vivi can’t explain what she’s feeling without sounding petty. My mother didn’t keep my artwork. I have no personal history to display. Savannah will no doubt say she’s envious because Vivi’s parents aren’t “all over” her. Vivi has what Savannah wants: freedom.

“Your mother doesn’t know I’m staying all summer,” Vivi says. “Does she?”

“I don’t care about my mother,” Savannah says, waving a hand. “Her opinion matters not. And you don’t have to worry about sharing my bed because…” She strides over to a door that Vivi thinks is a closet and opens it to reveal another bedroom, this one just big enough to hold a double bed, a dresser, and a desk set by a tiny window. Vivi gazes out—she can see the harbor in the distance. The tiny room is perfect. It’s compact and sensible. She can write here while looking at the water for inspiration.

Tears drip down Vivi’s face. “How long does she think I’m staying?”

“Oh, it’s this stupid family rule. Houseguests get one week.”

“Why didn’t you tell me this?” Vivi says. “You said I could stay for the summer.”

“You can stay for the summer,” Savannah says. “I just have to speak to my father in person.”

Mr. Hamilton lives and works in Boston during the week; he arrives on Friday afternoons and leaves on Monday mornings.

“What if that doesn’t work?”

“It always works,” Savannah says.

“But what if it doesn’t?” Vivi says. “Just give me the plan for the worst-case scenario.”

“Worst-case scenario?” Savannah says. “Listen, my parents never, ever come up here. And they go to bed early. We could just say that you’ve found a place to rent and that every once in a while you sleep over. I’ll take care of cleaning your room, doing the sheets, and whatnot while my mother is at the club—”

“You’re suggesting I hide here all summer?” Vivi asks. “Like…like Anne Frank?”

This makes them both laugh—but is it really funny, and is Vivi really so far off base?

After spending a few days on Nantucket—lounging on Nobadeer Beach, driving around town in Savannah’s bare-bones Jeep (no top, no doors, no back seat), riding a couple of the old Schwinns in the garage out to Sconset to see the first bloom of the climbing roses, dancing all night at the Chicken Box—Vivi is ready to consider the hidden refugee plan.

When Mr. Hamilton shows up on Friday afternoon, still in his pin-striped business suit—he’s the managing partner in a big law firm on State Street—the household becomes far more festive. Mr. Hamilton makes his famous frozen margaritas and they drink them while sitting at a table by the pool.

“How are you liking Nantucket?” Mr. Hamilton asks Vivi.

“I love it,” she says. “I never want to leave.”

“Ah, but leave you must,” Mrs. Hamilton says. “Monday, yes? Have you booked your ferry?”

“Can’t Vivi stay a few more days?” Savannah asks. “Please?”

“A few more days won’t hurt,” Mr. Hamilton says, filling enormous tulip-shaped glasses from the blender.