The notebook is on your nightstand, and it’s all that’s left of her in the thin morning light. It’s tattered—old blue cloth-covered thing, white cardboard showing through at the edges and corners. Looks like it’s ridden in her pocket for some time. You hesitate only briefly before opening it—probably private, yes, but maybe she left her address or phone number written in the front cover. You only got her name. Not any of her contact info. And you want to see her again. Never had a connection quite like that. Never brought a stranger home.

You open the book. You see your name.

***

I am thinking of you in the spaces between. Like always. Ever have been. Ever will be.

You don’t know me, but I know you. Or another version of you.

We met in this bar back home. You didn’t recognize me. That was a relief. All life long I’ve had cameras pointed at me—when I launch, when I return, when I go to the supermarket. But you had no idea who I was. That’s why I started talking to you in the first place. That’s why I went home with you.

(This isn’t the you I know. I know that. Forgive me talking about our life together, a life you’ve never had. I have to get this out, and you’re all I’ve got to give it to.)

You’d heard of the accident, of course. Everyone had. How the first passenger transport to use a Between gate didn’t come out exactly right. How fourteen of us survived—but changed. How we now have the ability to walk between worlds. Not a simple folding of spacetime, like the Between engine was designed for. But actually walking into the between, walking straight into another universe.

I was twelve. I got off the transport into a sea of cameras and haven’t really shaken them off since.

The government changed our last names to Walker. They took custody of us—yes, even the adults. They had to study us before releasing us back into the general populace, they said.

They never did release us, of course. Once they had figured out what we could do? There are things the government deems too dangerous to release into the wild. So we got studied, poked, prodded.

Drafted.

Of course we were drafted. We could complete missions no one else could. They didn’t need to risk dropping soldiers into a war zone to retrieve items of strategic importance. They had us. All we had to do was walk into the next world over and retrieve the corresponding item, or just pinch a fold and walk through into our world, in another place and time.

“What is it really like?” you’d asked.

What is it really like?

It’s a little like dying, I guess. It’s a little like floating. It’s a little like a dream. It’s a little like a lot of things.

We walk.

We concentrate. We bring up the Between—that great greyness we were trapped in forever, for moments that felt like forever.

And we walk through.

There is no time there. There is no horizon—none of the things that you can use to orient yourself. There is no thought—or very little. No conscious thought, anyway. Your minds wander where our bodies do. We walk through dreaming. We come out elsewhere—different places or times in this world or, more frequently, worlds beyond most people’s imagining. A tiny thing changes so much. One small choice shifts a world—not just voting for someone else, but leaving your wallet at work, getting a cat instead of a dog, wearing the red dress instead of the blue one—and everything changes.

Just like when I met you. Everything changed.

I had never known anyone like you. I had hangers-on. I had starfuckers. And oh, man, did it take me forever and some hard lessons to learn that they only wanted me so they could brag to my friends that they were screwing a Walker. That took a lot of crying.

But you only wanted me. Just Sarah. Just like I was any normal girl. Not a celebrity, not a Walker, not the wielder of some mysterious power. Just Sarah, just this girl you liked and, later, loved.

And we built something of a life together. It was a life punctuated by Walks, but hey, lots of couples have to deal with one partner’s business trips. It’s just that mine were to places you couldn’t go. And I’d have an increasingly long refractory period. I used to walk back through and just go on with my life. Then aches and pains for a day or two afterward. And the last few times, I pretty much collapsed straight into bed for a day or two.

You got my grandmother’s beef barley soup recipe. And you made me tea. And you curled up beside me and watched movies with me. When we slept, you curled around me, twined your leg in my legs, wrapped your arm around me, loose fist against my heart, and I would fall sleep holding your hand to my heart.

We didn’t talk about it much. The sickness. We knew instinctively that there had to be a price. That that sort of massive change on the cellular level is going to lead to unforeseen consequences.

And I kept Walking. What else could I do?

***

Here’s a secret: the one thing I’ve never told you-prime. Or, well, one of the two. But we’ll get to that.

I have carried this book with me through dozens of worlds; after every mission is complete I sit in Jack’s bar and scribble in it and wait for you to come to me. You always do. Something in every version of you responds to something in me. I ache a little for you, for that—the accident erased me through all worlds. Erased me, or coalesced all of the possible mes into this me.

So I can take my little samples of you, and go home to my you—and if, the morning after, you couldn’t stop thinking of me—if you fell half in love, as I always fall in love with you—

I’m sorry.

I’m sorry for giving you just a fragment of something you can never truly have.

Mea culpa, mea culpa, mea maxima culpa…

I tell myself it’s not cheating if it’s the same person. And it is only ever you. All my life, in all of my worlds—I screwed around plenty before I met you, had the usual slew of infatuations, but nothing like what I had with you. Never a love this strong.

So I seek you out. I study you, the way you would’ve been if your life had been different. The way you would’ve been if you didn’t have to take care of me.

I fall a little in love every time. And every time, I end up back in your apartment, back in your bed, my hair falling all around a different you, your hands with their calluses in the wrong places, your missing scars.

***

Perhaps it is my biggest act of cowardice that I can’t, won’t, give this to my you.

I used to call my you the real you, when I started this book. But, with every walk, I’m more and more aware that every you is the real you.

So my you is you-prime. Which sounds silly. But it’s the language I have. And here is my other secret. The only other thing I’ve ever kept from you.

Dear You-Prime—

I’m not coming back.

I want to. More than anything. I want to go home. I want the Incident to never have happened. I would gladly trade all of the Walking, all of its marvels, for a quiet normal life with you. A cottage on the beach, maybe. With a dog. Maybe a golden retriever.

But I’m not coming back. Not from this walk.

It was about three years ago that the first of the Walkers stopped returning. Cal—remember Cal? We were so puzzled when he never came back. It was a standard walk, no tricky stuff. To an alternate he’d been to before, even. But he never came home. We figured maybe he defected, maybe he found something over there he couldn’t get here.

About six months later, it was Jeff.

Then Kelly.

That much, my version of you knew; I told you we probably had a defection epidemic going on. That’s what we all thought for about two years. Which is why Command implanted us all with tracking chips—so if someone tried to defect, we could track them down and bring them home.

But when Dana disappeared…her chip died. Lost cohesion, lost signal. And that’s when the scientists started to go oh shit. That’s when they started calling me in for all those physicals. Full-body scans. That’s when I started to feel less like a courier, more like a lab rat.

That’s when they started to figure out that the walks were taking us apart. Walkers weren’t defecting. They were…dissolving. Into the spaces between. Each Walk accelerated the inevitable breakdown.

When I got sick…they knew what it meant. Marcus had gone just a month prior, and they’d been taking samples from the remaining walkers since Dana had died, so they saw the progression in Marcus.

And they’ve seen it in me, and they’re pretty sure—as sure as you can be with a mysterious illness and a tiny sample size—that I’m not coming back from this one.

I’m going to try.

I could settle down with this you and try to make a life here, hope the illness doesn’t consume me. Hope I don’t dissolve into thin air, become foam on the sea. And I considered it. But it isn’t the same. No you is my you. And I don’t know how I can live without ever seeing you again.

I don’t want to go.

But I don’t want to run away, either.

Maybe when the last Walker dies, the worlds will snap back into place. Maybe there will be another me for you.

Soon, now. Soon you’ll get to see what happens.

As for me, it’s morning. And I have a Walk to make. At least, I hope I do.

Love you ’til the stars go cold,

Just Sarah

***

I am thinking of you in the spaces between. I always have. I always will. The between will shortly be all there is of me, and all there is of me will be a memory, a dream, of you. Of a you I knew worlds ago and worlds away, a you I’ve carried with me in my thoughts through a hundred bars, a you who’ll never know what became of me.

I am thinking of you in the spaces between.

I am thinking of you in the spaces between.

I am

Between.