You wake up, and I don’t know where I am.

You’re flat on the grimy station floor. Cheek mashed into the hard metal, the taste of artificial gravity sharp on your tongue. Your eyes are streaming with tears.

There’s a raging wind.

“Fuck.” You crank one eye open and blink groggily at the wall several feet away. The heavy-set door is clamped shut, but the wind roars around you like a hurricane delivered directly to your doorstep, and you can barely move for the force of it. But the door is shut.

The door is shut.

“No.” You scramble to your feet—or try to. The wind buffets you back, nearly knocks you down again, but after a moment of blind panic that hits like a fist—there’s a hole, there’s another hole in the station—you flail to your feet. This checks off two things. One, the gravity is still roughly earth-standard, and two, since you haven’t passed out, that reinforced door is doing its job. There might be a hole outside the testing facility, but not here, and that’s good, because the only opening you want to see inside this grubby, dimly-lit room, is—

Wait.

“Oh no—” You spin around, nearly trip over your own feet, and locate the source of the wind.

The room is a perfect square, gray-walled and bristling with monitoring equipment directed at one thing. In the center of the room, about five feet off the ground and floating serenely—or at least it’s supposed to be—is the dimensional tear.

I gasp.

No. You gasp.

No—I gasp. The sound escapes your lips but it doesn’t come from your mind. It’s distinctly mine, but I don’t know who you are. And you don’t know who I am.

“Stop!” you tell me, or maybe you’re directing those words at the multidimensional tear—what my team calls Delta 2Xb—because that tear is looking less like a few popped stitches and more like a giant rip in the fabric of the universe. It’s a spinning, spasmic blob of incandescent light, which is probably very bad, because the only time I ever saw Delta 2Xb glow, I nearly died.

That was six months ago, and I’m not keen to repeat the experience.

“Neither am I!” you say out loud, and then you flinch like you want to reel it back in. Your whole body fuzzes with panicky static, right down to the fingertips, and I feel it as if through a thin sheet. It’s not mine, but yeah, I’m about ready to panic.

I don’t want to die. Not here. Not when—

“Stop thinking that!” you shout and clamp your hands over your ears. “For god’s fucking—fuck!”

Whatever admonishment you’re about to give, it never makes it off your tongue. With a sudden burst of garishly white light, Delta 2Xb spasms, spinning a lash of violent wind through the room, and as you stumble back, it vanishes.

That’s it. Like a star winking out. Like a lightbulb filament bursting. The project I’ve been working on for two years is gone.

And I am stuck here with you.

But I don’t know who you are.

You stand in stunned horror. It’s an old horror, I collect dimly, hints of something terrible and familiar reeling beneath the surface, but when I try to dig a little deeper, you clamp down so hard I flinch.

“What happened—” I start to ask. You don’t answer me. Instead, halfway through, your mouth forms different words. Like a skipped track.

“It’s gone,” you mumble. “It’s just…gone. My work—”

It’s my work too, though. A project I’ve dedicated my life to, taking a one-way trip from Earth at the age of twenty-nine. How could you? How could I? Nobody would. And somehow, they got six of us to volunteer. Young, unmarried, no next of kin, brilliant and eager to deliver an astounding discovery to a dying, hopeless planet. So I made my way into space with five other people I barely knew and followed a distant, mysterious signal, hoping to reveal the secrets of the multiverse.

“What happened?” I ask you again. I’m all twitchy and uncomfortable, your scalp itching and spine tingling, and I want to move my limbs but they’re not mine. I feel like a Russian doll, crammed inside something else, and I’m becoming far too aware of it.

Your heart rate picks up, but that might be me.

At my words, issued from your lips, you jerk to life. Briefly, you’re annoyed at my ability to use your mouth, but then the confusion hits.

“I don’t know,” you manage. “I don’t. I—oh god. I really don’t know! I need to—”

You lurch toward the central control panel on the opposite side of the room and start jabbing at the buttons. You’ve got loads of devices, everything designed to dig into that nebulous space between worlds, inside this tiny testing facility, which has been reinforced and in turn surrounded by a space station designed entirely for Delta 2Xb—but that’s not the odd thing. I know these controls—every single one of them. Hell, I’ve run so many tests here that I could do it in my sleep.

The odd thing is that these controls are dusty and sticking from lack of use.

You’re still working them, thumbing the buttons with an ease I recognize, but my station has six people for a reason. There’s just too much to do.

Somebody should be communicating with us right now, but nobody is.

Unease prickles down your spine, but this time I can tell it’s mine. I turn, casting your gaze across the testing facility, noting the oxygen readings on the wall, the heavily reinforced door. We reinforced ours the same way after the Morric incident, and—

“Ow!” The word—my word—slips from your lips as you snap your gaze back to the controls.

“Stop looking around!” you growl. “I have to figure this damn thing out! I don’t know who you are—“

“I don’t know who you are!” I counter, which is weird as hell. Your tone changes mid-sentence, the register rising with my frustration. “I don’t know how I got here! I was just running the routine tests and—hey, listen to me! Listen to me!”

In angry desperation, I reach out to grab you and don’t make it. Instead, it’s your hand that jerks, and we lunge together into the controls, smashing your nose on a panel of buttons.

It definitely feels like my nose.

“Ow,” we groan. You grab the edge of the slim control panel and heave yourself to your feet, then turn and sag against it. The edge digs into the stiff back of your semi-protective suit.

“What. The. Fuck.” You enunciate each word into the stale air. The wind has died down utterly. It’s almost eerie. There are three fluorescent strips on the ceiling, but unlike my station, only one is lit. It flickers mournfully over a room empty of the only valuable thing it held. You stare at that flickering strip, then raise your hand to block it out.

It’s my hand. I should know. I’ve had it my whole life. Thin, pale in the weak lighting, with a small scar I got from my childhood cat, Scratchy. It runs the length of the lower thumb and sends a terrible jolt of recognition through me.

“Oh my god.” It could be you saying it. It could be me. In this moment, there’s no sheet between us. I feel the entire awful revelation of it, your heart pounding like it’s mine. “Oh my fucking god.”

Your hand—my hand—is shaking. You clench it into a fist, the knuckles popping white.

Then you lunge for the door.

The space station we run through looks like my own, if somebody forgot to clean it for several months. The floor is so dusty you nearly slip twice, and though Jeffrey loves to paste band posters down the hallways, all I see are tape markings across the battered gray surfaces. The bathroom we stumble into is cramped and grimy, the toilet a dim silver, the light as weak as that in the testing facility. An eerie sensation of disuse drapes over everything.

“What happened here?” I ask you. You don’t answer. Instead, you splash cold water on your face, grip the edges of the square, metal sink, and stare into the spotted mirror, your eyes searching for an answer.

You find one immediately. No—I do. Because that face is mine. The semi-suit’s hood is down, so I’m face-to-face with my short, clipped brown hair, wide nose, and dull brown eyes. My skin is washed out and sallow with a couple of familiar acne scars still hanging on from puberty. My eyes are bulging and red-rimmed. I look like I’ve seen a ghost.

Or maybe that’s because I am one. I don’t ever remember looking so dead.

“What the hell happened here?” I ask again. You clamp down on the words. There’s a funny lump in your throat, like you’re trying not to cry.

“This can’t be happening.” Your voice comes out cracked and hollow. You speak to the mirror, but decidedly not to me. “This is insane. I was just running the routine checks—”

Your fingers dig into the sink, hard enough to draw the horrible screech of metal. Your eyes bore into the reflection, and for a brief moment I catch myself there, our expressions warring for space on the same face. “Just the routine checks,” you repeat. “That’s all I do these days.”

This sets off an alarm bell. “What do you mean, these days?”

You don’t answer. There’s something tight in your chest, a crack in a dam that you refuse to let break. I can feel it all in that distant way, separate but right up close, and it makes me want to dig my fingers into your brain and figure it out.

But if you’re me, I would hate that.

“It changed,” you continue. “Right before…this happened.” You wave a vague hand toward the reflection.  “It changed, and I knew I should have—I don’t know. I thought it was the goddamn Morric thing again, but I didn’t even—“

“The what?” You blink—I blink—in recognition. Then you shake your head a little, thoughts shuttering like a window.

“No.” You drop your gaze to the sink. “No. This isn’t that. It shouldn’t be—“

“Be what?” I raise your hand and press your palm against the mirror, as if to cut you off. “Are you talking about the Albert-Morric measurements? The incident?”

You stare at me, dead-eyed and suspicious. For a long moment, you don’t answer.

“Who are you?” you ask at last. “How did you get in my head? You sound like me, but you can’t be.”

I give a quiet laugh; your reflection mirrors it. “If I’m right, you’ve spent two years running tests on a spot where the walls between universes rub thin. You look exactly like me. If we’re the same person…yeah, I’ll play along.”

You stare at me in the mirror. “I don’t need the sarcasm.”

Your eyes drop once more to the sink, head ringing with discomfort the way it feels to be watched over your shoulder. But I can’t help it; I have nowhere else to look. “Not now, okay? I don’t need company.”

You sound defensive, but it’s not even the tone that gets me—it’s the wording.

“Sounds like you don’t spend much time with your team,” I say. At this, you tense violently, and memories whirl by like thin sapling branches caught in a wind, but before I can understand them, you tighten your grip on the sink and lock them down.

“If you’re me, then you know they think you’re a loser,” you mutter. “That’s not true!” I protest, but you turn abruptly around and settle against the sink, which creaks in annoyance. You cross your arms and stare moodily at the toilet.

“You have to get back,” you tell me. I nod your head.

“I want to go back,” I say. “But why not ask the others for help? Where are they, anyway? Moira usually runs the routine checks, at least in my universe.”

You swallow hard and don’t answer for a long moment.

“The others left,” you say. “There was an issue. A weird signal came up on a passing asteroid and Jeffrey organized a trip on the emergency craft. I’m watching the place until they get back.”

You’re so obviously lying that it’s almost scary to see. You’re forcing a false truth down my throat as if my acceptance of it is life or death, and it’s…not fun to watch. I’m in your head, but I might as well be behind a big locked door that says KEEP OUT. Angry red warning lights and everything.

I shiver a little, not from the stale, drafty air, but from the tension of knowing I’m in the same room as…I don’t know. A liar, definitely. Something worse? I hope not. I’m not the kind of person who can keep a lie going for long. I don’t wear guilt well, and it radiates off you in waves.

What could be so bad that my own alternate self doesn’t want me to see it?

I force you to straighten, ignoring your annoyance.

“I have an idea,” I say, turning with false brightness to face the mirror. “You were in the testing facility during the Morric incident, right?”

You nod uncertainly.

“Well, by the time I got everybody safe, Delta had disappeared, remember?”

You nod again, but you’re wearing an expression that I can’t place. Which is funny—I never took myself for the bashful type, and definitely not over this. The Morric incident was both the most terrifying event of my life and easily my biggest accomplishment.

“But it came back,” I continue. “After a few hours, Delta came back. We monitored everything. I bet you did too.”

Another uncertain nod.

“So,” I say, “Let’s compare notes and see what happened. And see if we can use that data to get me back. Sound good?”

You open your mouth, hesitate, then shut it again.

“What if you can’t?” you ask. Your face has taken on a distinctly unpleasant look, which would be insulting if I didn’t share the sentiment. I don’t think I like myself that much.

“Trust me,” I say, “I’m getting out of here.”

Somehow, that doesn’t make you look any better.

Your footsteps echo down the tiny station hallway with a trepidation I don’t understand. I want to dig deeper, but I abstain out of both respect and a separate goal: I want to figure out for myself what I’m missing.

You don’t like this goal, I can tell, which only makes me look a little harder. The station is a circle with many spokes, the testing facility at its center. The ceilings are paneled with lights, half of which are out. The decor is mostly just equipment mounted on the walls, except for those bare spaces which held Jeffrey’s posters, and the floor is so dusty. In a self-contained living system in space, cleanliness is deathly important. If you’re not a neat freak, you might be spelling your own demise when too much dust gets into your systems.

That’s very weird, but what’s really putting me on edge is that, theoretically, this is not how traveling between worlds should work. Delta 2Xb is a weak point between nearly identical worlds. The worlds closest to each other are supposed to differ in minor ways. A left turn instead of a right. A rock kicked down the road. Not the great big spooky absence of five other people who are…gone. On a trip, supposedly.

“Can I ask—” I start as you step into the testing facility, but you talk right over me. Pointedly.

“I want to get this over with. Let’s just review our data.”

“Fine.” I resist the urge to be petulant. Your feet guide us to the opposite wall, and you touch the trackpad that lights up our little data center. It’s no more than a military-grade monitor, the screen scuffed and worn. “So, you know what we’re looking for?”

“I have an idea.”

Your eyes are glued to the screen, so mine are too. You navigate back to that fateful day six months ago and click on the file. It’s a big one—we film everything and collect every bit of data. “You think that the Morric incident made Delta unstable,” you say. “I—we—took a break from running tests for a couple weeks after, but—”

“We did too, but we started up again,” I say. “And if we’re this close to each other, universe-wise, running tests at the same time, I bet we screwed it up again, in the same way. Let’s check the video.”

I move your hand across the trackpad, and for a moment, you let me. Then, with a jolt, you drag the cursor away.

“No!” you say, too loud. “I mean—video isn’t important. We need the notes. Let’s start from yesterday.”

“But—” I begin, but you’re already doing it, and you have just a little more control than I do. I also don’t want to ram my nose into the control panel again, so I swallow a sigh and allow you to navigate.

But I don’t like it, and I think you can sense my unease, because the hair on your neck stands on end.

The next three hours are boring and incredibly tense. We work together, which means we argue a lot, running through the data and swapping experiences and comparing notes. It’s infuriating, because as near as we can figure, we’re right.

If we’re telling each other the truth—I know I am—and our notes match up, then something we did to Delta caused it to shut. Worse, I was the one working on it in both universes, so either way, this is our fault.

But theoretically, good old Delta should return like it did after the Morric incident, and if you bring me up close, the reversal will probably happen. We’ll separate, and I’ll wind up back where I belong.

This is what I’m hoping. I don’t want to consider any other alternatives.

But after three hours of stooping over a small, dim screen, blinking at notes and trying to make your brain work, not only has Delta not come back, but you’re pissed, and so am I.

“It doesn’t make sense!” you huff as we encroach on hour four. With an angry breath, you grip the edge of the control panel and rock back on your heels, burning with irritation.

“I know, I know.” I want to grind your palms into my eyes so hard I see stars, but you’re too busy clutching the control panel. “We have to keep going. I’m not going to be stuck here.”

With you, I don’t add. With you and your creepy, dirty space station, with your missing teammates and your weird, defensive walls. I’m starting to think you’re a serial killer.

“I don’t want you to be,” you growl. “But we’ve looked at everything. Everything. There’s nothing else to do but wait and hope.”

You release the control panel at last, so I take your hands and rub them over your face. I’m tired as hell, and your body is aching. Your shoulders are stiff, your feet are sore. You’re hungry, but neither of us want to leave the room. “When Jeffrey and the others get back, we can tell them. Maybe they can—”

“They won’t believe us,” you say so fast it startles me. “No, we have to get you back. Fast.”

“What?” I ask. There’s something pressing behind your walls, I can almost feel it. A truth so close to coming out.

I need to know.

“No!” you shout. “That’s—they wouldn’t believe us! They don’t even like you, they’re standoffish, and they’ve been that way ever since the start—”

“That’s not true,” I try to interject, but you keep going.

“Yes it is!” you insist. You rock forward, hand pressing into the control panel. Your eyes flick to the monitor again, almost in fright, and I notice we’re back on the day of the Morric incident. Video and everything. “They didn’t—I mean, you know we’re not good with talking to people, but they never— They never—”

With a start, I realize you’re talking in past tense. It’s not even a matter of words; I just feel it in your head.

“Nothing.” You shake your head again. There’s something boiling to the surface, something so close to grief it hurts. “God, it—this was a mistake. Coming on this trip. I knew it was going to be one way, but I never thought it was going to be like this—“

“Like what?” I ask, but at the question, your hand curls and you pull away. “Hey—tell me!”

You try to turn, as if you’re in control, as if it’s your body, when we’re still the same damn person, secrets or no, and maybe it’s because we’ve been arguing for three hours, but I’ve had enough. Just as you turn, I lift your hand and lunge for the trackpad.

“Hey!” You catch me, but it’s too late. I only needed a quick click, and even though our opposite motions wrench us in a two-way stagger that sends us stumbling sideways onto the control panel, the video opens and starts to play.

I force your eyes to the screen as it begins—black and white, the time ticking in the corner. And it only takes two seconds to understand.

“Stop,” you plead, and fumble for a hand to slap childishly over your eyes, but I force it away.

It’s me on that screen, but it’s not how I remember it. We’re in the same spot when it happened—in the testing facility, suited up, when Delta goes haywire. But you’re not doing what I did.

In my universe, six months ago, the throwback from the Albert-Morric measurements tore a hole in the outer wall of our monitoring station. To this day, we don’t know how. But it was just large enough to drop the atmospheric pressure and ruin the oxygen levels, sending my crew into a sleep that would have ended in five nasty deaths if I hadn’t been there. In all honesty, I probably should have stayed inside that extra-reinforced testing facility, considering a semi-suit isn’t nearly good enough protection from depressurization. But instead, I ran out there like a reckless idiot, isolated the leak, and dragged them each to safety. In my universe, I acted. In this parallel world, on that tiny screen, I’m squashed in the corner of the testing facility as Delta spasms and spins in a whirling rage, and it looks like I’m trying not to cry.

“Oh.” The sound slips from your mouth, soft with horror. “You—“

Your hand slams into the trackpad, you scramble for two seconds, then the screen shuts off. Above the screen, almost tentatively, one of Delta’s indicators starts to flicker.

“You didn’t need to see that.” Your voice is shaking.

“They’re dead, aren’t they?” I’m too stunned to cushion my words. My whole brain is reeling, your body fizzing with my shock. “You’re the only one left. But I saved—“

“Yeah, well I didn’t!” Your voice catches on a sob and breaks. You sniff angrily, then wipe your hand roughly across your eyes. “You’re better than me, I guess. You made them like you, and you saved their lives, and I failed. And now I’m stuck here. Alone.”

You pull back then, just a corner of your shield, and in that moment I feel it all. The fear and the anger and the gnawing loneliness, a maelstrom contained in one body and two minds, but most of all, it’s regret. Regret and a horrible, horrible grief, because the only thing worse than a tragedy is one you could have prevented.

You stand there, motionless. In grief and shame, but I’m stunned. I have no words. On our neck, a thin breeze rustles.

“It’s starting to come back,” you sniff. As if in response, another indicator flares. “You can leave now. Go back to your friends.”

I still don’t speak. I can barely think, let alone process. When I don’t respond, you let out an angry breath, then turn around and jab a finger at the middle of the room.

“See? It’s here.”

You’re right. We were right. Delta is coming back at last, returned from its tantrum, and I have a chance to go home. To a mission I staked my life on, and my friends, the only real friends I’ve ever had, because I’m terrible at making friends. Even with myself.

In the silence, you turn back to the monitors and check the readings. There’s a pained determination in your thoughts, hastily papering over your barely-contained tears.

“Thirty seconds,” you announce. “Before you lose your chance. Walk right in, and we can forget this ever happened. Please.”

“It was my decision,” I realize. Before you, Delta coagulates in spasmodic, blinding fashion. “This is the closest universe. My choice split us in two.”

“Twenty seconds.” You’re practically begging, but our feet don’t move.

“Do you want me to take you back?”

I don’t know. Neither do you. You want friends as bad as I did, but you lost them all, and what kind of friend is your own double?

“Ten seconds,” you say. “You have to decide.”

“I know,” I say. “I know.”

Because I made the choice, and you didn’t. And now I have to make it all over again. It was worth saving my friends. I can’t decide if it’s worth saving you.

But what kind of person are you, if you aren’t there for yourself?

No, don’t answer that. I know what you would choose. It’s up to me now.

I take a step forward.