“You fell in love with me in another dimension,” he says without looking me in the face. “Maybe it was only ever Lieutenant Markov after all. Maybe, instead of being your destiny, I’m only a . . . stop on the way.”

Okay, I know we’ve both been through a lot, and Russians are fatalistic, et cetera, but this has to end. “Don’t say that! This is just the splintering talking, don’t you see? You’re ignoring everything we’ve done together. Everything we’ve been. Or was I never anything more to you than a math equation?”

That was supposed to be a rhetorical question. Apparently it isn’t.

“Math doesn’t lie,” Paul says. “Our emotions do.”

I’m too flummoxed to argue. Without some grand cosmological destiny tying us together, Paul . . . doesn’t believe in us.

He continues talking, staring at his own shoes. “We deceive ourselves into believing we can have what we want most in the world. But it doesn’t always work out that way. We know that now.”

“Stop talking about us like a physics experiment!”

“You’re not being logical about this,” Paul replies.

When a scientist tells you you’re not being logical, you have to get out of the argument immediately, because they’re recalibrating the scales to make sure you lose. I hug my knees to my chest as I curl in the far corner of my bunk. “Don’t you have some experiments to run with the Firebird?”

Paul looks like he wants to say something else, but instead he heads out, unhappy even as he has a chance to save the world. As soon as the door slides shut behind him, I grab my own Firebird and try to leap out of this miserable dimension.

No such luck. I’m stuck here, adrift in space, hopelessly far from home.

Valentine’s Day was only a few months ago. Lots of people, including my parents, say it’s a stupid fake holiday to sell greeting cards, and if you’re only reinforcing your relationship one day a year, you’re in trouble. I thought I agreed right up until the moment Paul brought me red roses and chocolate.

“I thought those were the right things,” he said as we snuggled together on the back deck, near the small fire in the cast-iron fire pit. We’d draped a single quilt around both our shoulders, bundling us together. That night, even the blue-and-orange glow of Josie’s tropical-fish lights on the deck railing seemed vaguely romantic. “That’s what they always show in movies. But on the way over here, Theo told me it was cliché.”

Paul had never had much of a love life before me, which is why he put so much stock in Theo’s advice. “Theo would probably give somebody craft beer and a trucker hat.” With relish, I plucked another candy from its crinkly wrapper. “And there is never, ever a bad time to give me chocolate. Remember this.”

He nodded solemnly. “Forever.”

“Do you like your books?” I was more worried about my own presents. Growing up surrounded by scientists, I had more or less absorbed the entire geek canon before I turned twelve. Mom and I had watched our way through Star Trek: The Next Generation together on Netflix, and Dad and I do a mean version of Monty Python’s dead parrot skit. But Paul—always grades ahead, without any kind of social life and surrounded by people older than him—had missed a lot of the fun stuff.

“I’ve heard of Dune,” he said, his gray eyes glancing toward the novels stacked at the edge of the firelight. “And I always meant to read Ursula K. LeGuin. But the compendium—what is it, the hitchhiking guide?”

“The Hitchhiker’s Guide to the Galaxy. Essential reading. And hilarious.” I leaned my face even closer to his, so that our noses almost touched. “You need to laugh more.”

“Never had as much reason to laugh before.” His broad hand weaved through my curls. “Nobody else ever made me this happy.”

“Same here,” I whispered. But loving Paul—it was as if he had lit a candle inside me, and that inner glow seemed to illuminate the entire world.

Paul drew me closer, kissed my temple, and whispered, “The firelight reminds me of the dacha.”

Our one night of passion. Back then I didn’t know the price it had cost. Back then, I reveled in the memory as pure hours of bliss. “Me, too. Let’s pretend we’re back there.”

His eyes brightened. I wasn’t suggesting we have sex on the deck—ugh, splinters—but he knew how much I wanted him to kiss me, and once we began kissing, it seemed like we’d never stop.

Valentine’s Day wasn’t even three months ago. Not long after, here I am, broken-hearted, unsure whether Paul and I will ever get back together, miserable. And in geosynchronous orbit. Yay.

My parents suggest that I have breakfast in the “mess,” under the theory that socialization is a good thing. I go early, just because I don’t think I can stand another second of moping around in the plain white box of my room. When I arrive, a breakfast shift seems to be just ending. Half a dozen jumpsuited people file out, talking to each other about solar flares and the breakup between people called Min-Ji and Cedric. One of them waves at me, and I wave back. Are we friends? Acquaintances? I guess everyone here must know everyone else.

One flash of blond hair makes me freeze. My brain whispers Romola—Wyatt Conley’s henchwoman in half a dozen worlds so far, including the Home Office. But no, this is someone else. The Spaceverse is one dimension where I don’t have to worry about her.

Looks like that’s the only lucky break I’m going to catch for a while.

As I sit alone at the cafeteria table, pushing reconstituted scrambled eggs around my tin plate, Paul comes in. His night must have been as sorrowful and lonely as mine, but his expression is so closed-off. Anyone who didn’t know him better might call him cold. Paul no longer expects to find any comfort with me, but I can’t help wanting it from him. My torn-in-two heart only knows that its other half is near, and yearns for him so desperately my chest aches.

Are we . . . broken up? The term sounds so childish for the terrible rift that has opened between us. When I think of it literally, though, it sounds closer to the truth. We have been broken. We are in pieces. We can’t be put together again.

He slides onto the nearest plastic bench. “How are you?” The way he says it makes it clear this is bare minimum politeness, period.

If he wants to talk about irrelevant stuff, then fine. “Well, this morning I found out that the exercise requirements on the space station demand three freakin’ hours of workout per day. Apparently it has something to do with bone density, not that I cared after an hour on the treadmill.”