"GO."

Dohyeok went.

He crossed the car in three steps. The white glove came down behind him, punch open, and Mu-hyeon's shoulder hit him mid-stride and shoved him the last meter through the doors.

Click.

The punch closed on air.

Dohyeok stumbled onto the platform, caught himself on a pillar, and spun around. Behind him the wall tiles said DAEHEUNG in old blue letters, and past the turnstiles there was an exit stair, and at the top of the stair there was light. Gray, soft. Like early morning.

The chime was still ringing. The doors were still open.

He looked at the doors. He looked at the stair. He looked at Chae-a.

Then he planted his feet on the platform like the argument was over, pointed one finger at her through the glass, and mouthed it slow so she couldn't pretend she missed it.

Wait for me.

The doors shut on her answer.

The train pulled away, and Daeheung slid off the windows, and our phones buzzed all at once.

[A passenger has arrived.]

[Binding has been extended. Remaining aboard: 6.]

"Oh," Haru said, very quietly. "Oh, it worked. It actually worked."

Baek-gu let out a breath that had been in him since Gyoha. "One down."

Chae-a didn't say anything.

She was still looking at the window where he'd been. Her hands were folded in her lap, one thumb pressed hard on the other, and her face was doing the thing it did during the deduction. Working.

"Chae-a," Minseo said gently. "He made it."

"I know he made it. I watched him make it." Her voice came out level. Too level. "Three months."

"...What?"

"We've been together three months." She turned from the window. "That's nothing. That's the part where you're still lying to each other about your favorite foods. You're supposed to get years first. Years of dinners and stupid fights and finding out he leaves towels on the floor. You're supposed to find out which way a person runs at the very end, when it barely matters anymore, because by then you already decided about them for other reasons."

Nobody interrupted her. Even the train sounded like it was listening.

"You're not supposed to find out this early." She pressed her thumb down harder. "I said go, and there was a monster's hand coming down behind him, and he got out, and he was safe, and the first thing he did was turn around and look for me. That's the whole test. That's the one nobody gets to study for. And now I know the answer about him, and he doesn't know it about me, and I have to sit on this train being someone who knows."

"He knows," Haru said.

"He can't. I haven't done anything yet."

"You said go." Haru shrugged. "He told us. First week we teamed up at the kindergarten, he goes, that's my girlfriend, she's the smart one, if she says run you run. He decided about you a long time ago. You're just late reading your own file."

Chae-a stared at her.

Then she laughed. Once, wet, more breath than laugh, and wiped her eyes with the back of her wrist like she was mad at them.

"Fine," she said. "Fine. I'll wait for the stupid stair with the stupid gray light."

Punch.

The sound came from the far end of the car.

Everyone went still.

The conductor stood over the last bench by the connecting door, glove closed around its lever punch. An empty seat. Nobody in it, nobody we could see, and it punched anyway, and a little crescent of paper fell and rocked on the floor. The eggshell face didn't turn. The slot in it breathed, in and out, patient.

Then it took one step up the aisle. To the next seat.

Punch.

"He's working this car," Minseo said.

Mu-hyeon was already on his feet. "Back one. Everyone. Slow, no running, don't brush him."

We filed through the connecting door into the next car back, and the sound followed us at its own speed, unhurried, seat by seat. Punch. Pause. Punch.

Baek-gu came through last and stood watching through the door glass.

"On a route," he said, "you get two kinds of slow. There's slow because the guy's lazy. That one you can work with. Then there's slow because the guy has all night and knows it."

Punch.

"He doesn't skip," Baek-gu said. "Look. Every seat. Even the ones with nothing in them. He's not looking for anyone. He's just... finishing the car."

...And when he finishes that car, this one is next.

I did the math on how many seats a subway car has and then stopped doing it, because the number wasn't going to help anyone.

"Then we don't need to beat him," Chae-a said. "We need to be gone before he's done. Everyone's signal is mapped. We wait, we listen, we leave. That's all this is now."

"Dalbit's next," I said. "Real Dalbit. Nobody's stop."

"So nobody moves," Mu-hyeon said. "No matter what the wall says. No matter what it calls out."

The train began to slow.

We lined up along the windows without deciding to. Tunnel dark, tunnel dark, then tile. The platform came up lit and empty, and the letters slid past and settled.

DALBIT.

The doors opened. The chime rang through an empty station. Somewhere down the platform a vending machine glowed by itself.

The slot opened.

"Now arriving, Wonseo."

Baek-gu twitched.

His whole body did it, one hard jerk toward the doors, and he caught himself with both hands on the rail like a man grabbing his own collar.

"Not yours," Minseo said quickly. "Your signal is Haedong. Wonseo out loud means we're AT Dalbit. It checks."

"I know." His knuckles were white on the rail. "I know. It said my street and my legs answered before I did. That's all."

The chime ran out. The doors shut. Dalbit slid away, clean, and nobody had moved, and the rule had held.

Twice now. Wall says the true name, voice says one ahead. Saejae, Daeheung, Dalbit. Three for three.

"Okay," Haru said. "Okay, so we've got it. It does the thing, we know the thing."

She said it light. But she was looking at the black window, not at us, and her reflection in it wasn't smiling.

"Haru?"

"Mm. I keep thinking about the reading corners."

"The what?"

"At the kindergarten. Each corner shelters once, remember? The corners worked. That was the whole point. They worked and they worked, and everybody learned corner equals safe, and then the night got long and the corners started being used up, and the thing that almost got someone wasn't the fox." She turned around. "It was a corner that had already been spent. The safe thing, gone bad, with the safe feeling still on it."

Punch, from two cars up. Faint now. Still coming.

"Everything in this city is a teacher," Haru said. "That's what I keep chewing on. It teaches you the pattern first. For real. No tricks, honest lessons, over and over, until you trust it. Learn the pattern, trust the pattern." She tapped the window glass once with one finger. "And then the pattern was the trap. The lesson was the whole setup. It spends three stations buying your trust because trust is the thing it plans to spend."

"Rule five," Chae-a said slowly. "This train does not announce its stops truthfully."

"Yeah. And everyone heard that and watched the voice lie, and figured the voice was the whole lie." Haru hugged her elbows. "The rules never said which part of the train does the lying."

The car got very quiet.

I wanted to tell her she was overthinking it. I wanted to, and I couldn't, because the cold spot between my shoulders agreed with her.

The train picked up speed out of Dalbit. The floor leaned back. Under us the motors changed pitch, working.

Baek-gu's head came up.

"There it is," he said, half to himself, almost fond. "The hill."

"The what?"

"Between Dalbit and Wonseo there's a grade. Long one. I ride over it topside every single night, the company hates it, second gear the whole way." He patted the wall of the car like it was a coworker. "Four minutes, this stretch. Bit more with a full train. It's the longest gap on the whole line, I could run it with my eyes shut, I know it like I know my own..."

He stopped.

The train was slowing.

The lean went out of the floor. The motors dropped, wound down, that long sigh a train does when a platform is coming, and Baek-gu stood in the middle of the car with his mouth still open around the end of his sentence.

"No," he said. "No, no, hang on. That was ninety seconds."

Light outside the windows. Tile.

"Dalbit to Wonseo is four minutes. There's a HILL. We never climbed the hill. I'd feel the hill in my knees, I feel it every night of my life. That was ninety seconds, flat, no grade." He turned to us, and there was something terrible in how reasonable his voice stayed. "You don't move a hill."

The platform slid up alongside. Lit. Empty. The letters came out of the dark one at a time and stopped, centered, in the window right in front of him.

WONSEO.

His stop. The wall, the true thing, the thing that had told the truth three times in a row, saying his name at him.

The doors opened. The chime rang.

Nobody breathed. One thing left. The rule said the voice speaks one ahead. If this was real Wonseo, the slot would say Haedong, and the pattern would hold, and he could walk out of this train and go home.

The slot opened.

"Now arriving, Haedong."

Baek-gu made a small sound.

The wall said Wonseo. The voice said Haedong. The rule held, the pattern held, every lesson the train had taught us stood in a row and pointed at the open doors, all of it in agreement, all of it saying go.

Everything agreed.

Everything except ninety seconds, and a hill that wasn't there, and one tired delivery rider's knees.