“I knew all of this meant there was no getting to Beau. But even when I went away to graduate school, I couldn’t get him out of my head, what had happened to him and whether there was some way to undo it. He’d been losing track of time before my Closing happened, as if the resealing of time was making him less and less real. That was the first hint for Alice and me that Beau’s world had collapsed alongside the wormhole within me—that the Opening was, in effect, the beginning of an alternate timeline, and the Closing was its end. All of our later subjects found that, leading up to their Closings, the same thing happened to those they’d met in their alternate realities. They lost time, like Beau. More and more of it, until there was no more to lose. It may be conjecture, but it’s conjecture in which even Alice Chan was confident: We are the door to Beau and his world, Natalie. When that door closes, he’s gone. When it closed inside me, he was gone.

“I did my best to move on. I married my grad-school boyfriend, did work that I cared about, poured myself into meaningful friendships. Still, I didn’t want to accept that Beau was gone, so I kept searching for a way to get to him. Eventually Alice realized I’d been going about it all wrong. Unable to move time anymore, I was never going to find Beau. My only hope was to be found in time. So I bought my parents’ old house and fixed it up, returned my childhood room to its original state to the best of my ability—so it wouldn’t scare you if you showed up here—and waited.”

“Waited?” I hear myself whisper.

“For you,” she says. “To find me. In the meantime, I started teaching at the University of Cincinnati. I commuted so I could keep working with Alice and her new subjects, who revealed another piece of the puzzle: the physical sensations of time travel. When moving forward in time, subjects felt a pull in their abdomens, like they were rising upward. When moving backward, they felt as though they were falling. Pretty obvious, really, but what we hadn’t documented before was that the physical sensation of entering the Other World always matched that of moving forward, while the feeling returning to your own world matched that of moving backward.”

I shake my head. “I don’t understand. What does it mean?”

“Time is an illusion, Natalie, relative to the person experiencing it. There’s the overall timeline of the world—dinosaurs, Ice Age, Middle Ages, Elizabethan Era, et cetera—but then each person experiences their own unique time stream as well. For most people that’s just a tiny section of time within that overall timeline. For people like us, it’s different. Our time streams can include excerpts from outside our linear lives. Think of arriving at our Senior Parade. Five minutes into our future, we were going to see buffalo where the school should be. That was our future, a moment occurring decades, if not centuries, in the past.

“Sometimes, you move through time and see everything changing before your eyes. Other times you lurch, or slip. That’s what used to happen to us as a little girl. Our body would wake up in the middle of the night, but our dreaming consciousness would lurch to a different time: a hypnopompic hallucination. You didn’t see yourself passing through every moment. You simply arrived, in my present, like you were locking on to me. That’s what you do when you go to Beau’s world. You jerk forward, as if you’re stepping over ripples in time to a point in the future.”

“Forward?” I say.

“You feel it, don’t you? The same sensation as passing into the future?”

“Beau’s in the same year as me, same day even—how can that be a future?”

She exhales. “We’ll get to that. Anyway, shortly after we made the discovery, Alice passed away. I was alone by then, my husband gone, and I almost gave up on you ever coming. Then one night, while I was sitting in my rocking chair, you found your way to my present. I knew from looking at you that you were around eighteen, probably already in the summer we met Beau. You only held time there for a minute before you lost your grip again—your Closing was close, after all. I was so caught off guard. I tried to comfort you, but I didn’t even know if you could hear me.”

That was the night of Matt’s accident, the last time I saw Grandmother. Though for her it was the first. The fear of that night, of tonight, crushes against me even as I remember.

“I spent years waiting for you to find me again. I thought if I could just see you one more time, I could at least steer you to Alice sooner. When I saw you next, though, we were further back in your own time stream. You were so little, and I didn’t want to scare you—I didn’t want to push it, so I just told you a story, one of the hundreds I’ve spent my life studying and teaching. It was the most natural thing in the world to tell you those stories, because I knew what they meant to me already and what they would mean to you someday. That night you listened, and then, after forty minutes, you were gone again.

“But a moment later you reappeared, and you held time there while we talked. It started skipping, like a scratched disc. I’d tell you a story, and then you’d lose traction. Those visits were far apart for you—six months or a year each. But for me, only minutes passed between them, as if your dreaming mind kept bringing you straight back to my time whenever it could, picking up where we’d left off. I watched you grow up in a matter of days.

“And as I said, I knew by then I’d never get to Beau again—has Alice explained the many-worlds interpretation to you yet?”

“I . . . I think.” My voice comes out as little more than a squeak. “She drew time with a bunch of branches. Each was a different world, I think; I mean, we’re talking about Alice, and she was in a science trance, so I’m not sure.”

Grandmother cracks a sad smile and nods. “We believe that those branches are wormholes. As such, they have an expiration date. An alternate future may be initiated, but unless the person with access to the wormhole chooses that future, it will collapse. Imagine an envelope that’s been sealed shut. You run your finger across the top of the envelope, and that’s time: one straight path. Then you take a letter opener, and you slice open an inch across the top.

“Now, when you run your finger over the envelope, there’s a portion where there are two separate paths, forming an ellipse. That’s the time between your Opening and your Closing. Say you run your finger partway up one—the current version of the world—and then decide you want the other one instead. You jump back to that initial split and change the course of events to take the other path. When we arrived at the Senior Parade, the venture into the past was a part of our future, just as Beau’s world—his alternate version of the present—is a part of your future. It’s the present when you look at days and years, but it’s your future because his version of events hasn’t truly happened yet, not for anyone but you.”