“New Hampshire,” she says with a sigh. “We agreed that the long-distance thing was probably not going to work, and we should just call it good, you know, quit while we’re ahead, make a clean break of it, et cetera, clichés.”

“When did this happen? I mean, when did you break up?”

She looks simultaneously guilty and sad. “Friday.”

I feel like she punched me, which makes my stomach hurt even worse than the terrible hamburger. “Friday. As in two days ago.”

“Yeah. I thought I was fine with it, that it was a mature decision and all that, but I haven’t exactly been fine. I’ve been . . .” She searches for the word. “Struggling.”

“You didn’t tell me.”

Her eyes meet mine. “You had your own thing going on.”

The way she’s been acting makes a lot more sense now. Also: I am a crappy sister. “I’m sorry. You should have told me. I mean, we broke up with our boyfriends on the same weekend.”

“Yes, we did,” she says with a hint of a smile. “But we’re both going to be okay now. Trust me on this. We’re going to be great. You’ll see.”

In this moment I know this as an absolute fact: I can’t tell her about Mom and the affair.

If I tell Afton, not only will I ruin Hawaii for her and all the optimism she’s feeling about how fricking great we’re going to be, but she’ll feel like we have to do something. I know her. She’ll want to confront Mom. And if we confront Mom, the only thing that will happen is that Mom will feel like she has to do something. And the only something that she can really do is, like, confess. And then she’ll probably split up from Pop. They’ll get divorced.

I can’t imagine life without Pop. Or Abby. Because Abby goes with Pop.

I’m a terrible liar. My face is an open book, Pop always says. My voice does the catch thing. But this time I manage to pull it off. “You’re right,” I say steadily. “We’re going to be great.”

Abby comes running up to us, grinning and chattering, cheeks flushed with excitement, eyes bright with her simple five-year-old delight in the fact that dolphins are a thing that exist. “Oh my dog, I want to swim with the dolphins! Can I, Ada? Can I swim with the dolphins like those people are doing?”

Afton stands up. “Let’s go see, Abby-cakes.” She holds out her hand to our little sister, who grabs it. “I’ll babysit,” Afton says, another generous gift to me. “We’ll talk more later.”

Or we won’t talk more later, which is what I’d currently prefer. Not until I figure out how I’m going to deal with this. Alone. All by myself.