A Generous Amount of Theory

“You’re not going alone,” Mori said, for the third time that morning, in the exact tone he’d used the first two. “I already told you what I was going to suggest.”

“You suggested Sikorska. I heard you the first time.”

“She defended you in front of the entire committee.”

“She also hasn’t knocked on this door once since a rift spat out a pack of monsters and a familiar,” I said. “If that’s what an ally looks like the day after, I’d rather not find out what she looks like a week into an actual manhunt for a warlock.”

Ears turned toward the door instead of either of us, Kou, from the windowsill, hadn’t said anything yet.

“It isn’t only trust,” I said. “If my theory about the cost of this is right, I can carry exactly three through a slide. Not four. Bring Sikorska, and one of you doesn’t come.”

“That’s not a fact. That’s a theory.”

“I have a theory built on the same magic that got you across two years using nothing but Kou as an anchor,” I said. “I’ll take my odds over Sikorska’s schedule.”

“And if your theory’s wrong, and it turns out you can only carry two.”

“Then we’ll deal with that when we’re standing in front of it. I’m not, at this exact moment, going to plan around a version of my own theory where I’m wrong.”

Mori’s jaw tightened, and he didn’t say anything else on the subject. Kou still hadn’t said anything.

“I built the first stable window anyone’s ever built at fourteen,” I said, into the silence, because someone had to fill it and it wasn’t going to be either of them. “Not glimpsed. Not flickered. Held it, for as long as I wanted, on one specific person. Nobody else at that school could do that. Nobody at Vesperine’s done it since, that anyone’s told me about. If resonance sliding runs on the same instinct, and it does, I’m the only one of the three of us who’s ever actually had it.”

“That’s a generous amount of theory,” Mori said, “built on one demonstration. Again.”

“It’s my demonstration. I’m still allowed to be generous with it.”

Kou finally spoke. “Can we skip to the part where you’ve both already decided and get to the part where it’s actually useful?” He didn’t wait for either of us to answer. “How do we find her? The adjacent one.”

“Kathi-1.”

“That’s a name. It wasn’t the question.”

“It’s the part of the question I’m answering first. I’m not spending the rest of this saying ‘the adjacent timeline’s Katherina’ every time one of us needs her. Kathi-1. Settled.”

Kou’s ears flattened, which from him was very nearly an eye-roll. “You did this exact thing to Mori.”

“It worked on Mori.”

***

Nobody had an answer to that either, which turned out to be the more interesting problem.

“The rift in my room, back home,” I said slowly. “When I saw her. It was night there too. Not exactly the same hour, maybe, but close enough that I didn’t notice a difference, and I notice things.”

“You’re building a theory out of a glance you didn’t examine at the time,” Mori said.

“I’m aware. Kou saw the same second I did and hasn’t built anything out of it, so it’s the theory we have.” If the offset ran in hours or days instead of years, wherever Kathi-1 was right now wouldn’t be far from wherever I was. Her room. The lab. A classroom, if the hour was near enough to matter.

We tried her room first, because it was the least likely to have anyone in it to explain us to.

I planted the staff and found the seam the way I always did, leaning rather than forcing, except this time I aimed the seam at a place instead of a person, and the difference showed immediately: the window held for barely a second, thin and straining at the edges, before it folded shut on its own. Long enough to see an empty bed, made, and a chair nobody was sitting in.

“She’s not there,” I said. “Moving on.”

“You could look again,” Kou said. “Make sure.”

“I looked. It was empty. I don’t need a second opinion from myself.”

Mostly because getting there meant not being seen getting there and two bats, one of them a color-inverted copy of the other, weren’t built for looking casual in a corridor, the lab took longer to reach than to search. I opened the window just inside the lab door, behind a postdoc who didn’t look up from the logs any more than anyone had my first week. One second of workbenches on the other side, and nobody I was looking for at any of them.

“Classroom,” I said. “Though if there’s any hour-offset at all, it’ll be the wrong one.”

“Try it anyway,” Mori said. “We’re not exactly drowning in better ideas.”

The classroom that mattered was my own, since whatever class I was supposed to be sitting in at this hour, she should be sitting in too. I was not, at present, sitting in it.

“You’re supposed to be in there,” Kou said, once we’d reached the back door of the lecture hall, low enough that it didn’t carry.

“I’m supposed to be finding a warlock. The lecture will keep. I’m less sure about the timeline.”

I opened the window in the doorway, behind the last row, low enough that the one person facing us would have had to be staring at the door to catch it. Rows of heads, not one of them pink, and gone before I’d finished blinking.

***

Because it was the one place on campus where three of us standing very still and arguing quietly wouldn’t be mistaken for anything worth reporting, we ended up on the open ground behind the dormitories, where the grass gave up trying to be a lawn and the tree line started.

I sat with my back against a low wall and let myself, for one breath, consider that this might simply not work.

Kou and Mori, predictably, filled the silence with each other instead of me.

“—which is the part nobody explains properly,” Mori was saying. “It’s not hearing. Not exactly.”

“It’s not exactly anything,” Kou said. “That’s the whole point of it. You’re not listening for a sound. You’re listening for a shape the sound makes when it bends around something that’s using magic.”

“Everyone bends it a little.”

“Everyone bends it constantly. It leaks out of you whether you’re doing anything with it or not.” Kou tipped his head toward me without actually looking at me. “Hers has a shape I could find in a crowded hall with my eyes shut. Years of practice, admittedly, and no small amount of motive.”

“You can find her. Specifically her.”

“I could find her from across a courtyard before she said a word. I don’t recommend it as a party trick.”

I sat up so fast I nearly caught the wall with the back of my head.

“Say that again.”

Kou looked at me properly for the first time since we’d sat down. “Which part?”

“The part where you can find me by the shape of what I leak.”

“I can. It’s not flattering, if that’s what you’re hoping for.”

“I don’t need it to be flattering. I need it to be true of her too.”

Mori got there half a second before Kou did. “She’s you. Whatever your magic looks like leaking out of you, hers should look close enough to match.”

“So instead of asking the window to hold open long enough to search a room with my own two eyes,” I said, “I ask it to hold open long enough to send something through that can search for me.”

“A pulse,” Kou said, already unhappy with the shape of the idea before I’d finished it. “Small. Fast. Out and back before the window closes on top of it.”

“How fast does a window close?”

“About a second, based on the last three.”

“Then it needs to be very fast.”

***

The first attempt collapsed with the pulse still on the other side of it, which meant a rift’s worth of magic went somewhere and came back from nowhere, and Kou spent a solid minute glaring at the empty air where the window had been, wings pinned tight to his back, without saying a single word.

The second attempt, I released the window a half-beat too early out of pure nerves, and it simply didn’t work at all.

The third time, aimed at nothing grander than the patch of ground we were sitting on, which at least had the courtesy not to watch me be wrong, I held the seam as steady as I’d ever held anything, the same close, careful leaning I’d used on Wenzel, and let Kou’s pulse go through the instant it was wide enough to take it.

It came back, already further than either of the last two attempts had gotten, pointing flat and steady, dead into the tree line behind us. Not the classroom. Not the lab. Not anywhere I’d ever have reason to be standing.

The window sealed itself a heartbeat later, and none of us said anything for long enough that a bird somewhere in the trees decided it was safe to start again.

“She’s in the forest,” I said, mostly to hear it out loud, because saying it hadn’t made it make any more sense.

I had never once gone in. There’d never been a reason to.

Kou’s wings had gone rigid. “Then I suppose we find out what her reason was.”