Sael Dunmarrow had never owned a chart of the district.

It was one of the few things about himself he had ever been able to say with pride. The Office issued charts to the junior ranks: broad sheets of waxed vellum, ruled in squares, on which the canals were inked in blue and the bridges in red. He had received one at the age of nine, and had looked at it for exactly the length of time it took to memorize it, and had returned it the next morning unopened. He did not need it. He had the streets. He had every stone of every causeway, every mooring post, every plank that rocked and every one that held. He had walked the district four hundred and twelve times, and the district lived in him whole, in layers, the way a language lives in a speaker.

It was only now, standing at the lip of the old wharf with the flood tide forty minutes off, that he understood how little the district had ever asked of him.

"We need to divide," he said.

The party had come together at the head of the basin in the last of the afternoon light, summoned by Miyu's whistle and Haruto's shouting. They stood on the green stone in a ragged half circle: Hoshina Haruto, flushed and sweating, with a smear of something sticky down one sleeve; Sakane Miyu, grim, with a coil of rope over her shoulder; Tachibana Ren, white to the lips. And Arimura Suzu, a little apart, with her fist closed around something small.

He had observed that she did not open it. She held it the way one holds a coin in a pocket, to be certain of its presence.

"Three channels," he said. "The first and second feed the lodging quarter and the market. Both have grated outlets and a walkway above the flood line. If the girl entered either, she would have found a way out. I judge the probability low. The third runs under the old wharf into the under-wharf, a network of drains and refuges. It floods first. It has no grating. I judge the probability that she entered it as high."

"How high?" said Ren.

"Eighty-one percent."

"That's a number you made up."

"It is a number I computed. It is based on the button, the footprints, the nature of the sluice, and her stated character as reported by two witnesses." He did not raise his voice. "I have not been wrong about a tide in eleven years."

"You haven't been wrong about a tide," said Ren. His voice cracked on it. "You were wrong about the sluice. You put it in two reports. You knew it was out here, unfenced, and you let a sixteen-year-old go walking past it every day for ten days"

"Ren," said Suzu.

"No. He knew. It's his district. It's his whole job, to know things, and he didn't, he didn't do anything."

"That is correct," said Sael.

Ren stopped.

"The sluice is outside the permitted district, and I knew it. The post is inside. The gauge assignment was submitted to me on the second day, and I sanctioned it. I did not walk the route. I did not inspect the wharf." He said it as he would have read a column of figures. "The fault in the arrangement lies with the Office, which has declined to fence a hazard for nine years, and with me, who observed the hazard and filed a report. It does not lie with the representative."

"Don't," said Ren, thickly. "Don't you dare defend her."

"I am not defending her. I am stating the allocation of responsibility." He turned his head. "The representative did not assign the gauge post in ignorance. She assigned it with my approval. She counted. She counted four times that I observed, and a fifth when the bell rang. If the count had been the cause, the loss would not have been detected until the sixth. It was detected at the fourth. That is not the pattern of a leader who loses people. It is the pattern of a leader who finds out."

There was a silence on the wharf.

Ren's mouth opened and closed. He looked at Sael, and at Suzu, who was staring at the stone with her lips pressed together and very bright eyes, and some of the fury went out of his shoulders, and what was left looked, for an instant, very young.

"Fine," he said. "Fine. Whatever."

"It is not whatever. It is accurate." Sael drew a breath. "Now. You will take the first and second channels, with lamps. Hoshina, the first. Sakane, the second. Tachibana, the connecting walkway between them. At the first channel, go forty paces from the grating and look for the red post. At the second, count the steps to the cistern and turn right. You will find the walkways above the line. Call her name. If you find nothing by the sixth bell, you will leave the channels. You will not remain."

"And you?" said Haruto.

"The third."

"With who?"

He had not been going to say it. He looked at Suzu, and she looked at him, and the whole of the afternoon stood between them, clean and bright and impossible.

"I am going," said Suzu.

"The under-wharf is a hazard."

"I know."

"It would be more efficient"

"I'm going," she said. "You don't have to like it."

He did not like it. He wished to state this clearly, to himself, for the record. He wished it to be entered in the archive that he did not like it, that every calculation he made told him it was a mistake, and that when she said it, in that low steady voice, his own hands had gone quiet at his sides, and he had found that he agreed.

"Then you will follow my steps," said Sael. "Not my direction. My steps."

"I remember," said Suzu.

---

The inspection stair began behind the sluice, in a doorway so low that he had to stoop. It went down in a tight spiral, and after eleven turns the light from the wharf gave out, and the world became the lamp.

He carried it himself, a sealed glass globe with a flame the size of a thumbnail, and it threw their shadows out ahead of them on the wet curved wall. The air was cold. It smelled of iron and old weed and the green rot of stones that had never been dry. Water dripped somewhere in the dark, very slowly, with the exact rhythm of a clock that had been wound once and forgotten.

He walked, and the district came up under his feet.

It did not come as a picture. He had never understood the word when other people used it. It came as a kind of knowing, laid over every step like a second layer of skin. Twelve steps to the first landing. The ninth tread is cracked. The left wall weeps. The lintel at the corner is lower than it looks, and he had cracked his head on it at the age of ten, with a father's hand on his shoulder, a father's voice saying, mind yourself, counting the stairs aloud so that he would learn them.

He stopped.

It was a very small thing. It was a half-step, a hitch in his stride, and he covered it so well that he did not think Suzu could have noticed. But there was a hand on his shoulder in his memory, and a voice counting stairs, and it was a voice, he found, that he had no record of ever hearing.

He set the thought aside. He filed it under pending. He kept walking.

"Eleven," said a quiet voice behind him.

"I beg your pardon?"

"There were eleven turns. I counted." Her breath hung white in the lamplight. "I'm sorry. I'll stop."

"No." It came out sharper than he intended. He tried again. "Do not stop. It is useful. Continue."

So she counted. All the way down, quietly, in a small steady whisper, the turns, the landings, the cracked tread, and his own memory and her voice ran in parallel down the stair like two hands on the same rope. It was oddly comforting. It was the first time in his life that anyone had counted with him.

She was gripping the stylus. He had heard the click of it on the third turn, the small sharp snap of the cap against her thumb, open and shut, open and shut, and he had not looked round, and he had known at once what it meant. It was a tell. He catalogued it with the others: the hand that went to the empty pocket, the shoulders that came up around her ears, the voice that went flat and procedural when she was most afraid. She was afraid now. She was afraid, and she was keeping her voice level, and she was counting the stairs aloud for him, because it was what she could do.

He wished, abruptly and with great clarity, that he had a hand to spare.

---

At the bottom of the stair the under-wharf opened out like a throat.

It was a long vaulted tunnel, half the height of the tower hall, floored with a shallow skin of black water that came to the ankle. Arched openings ran off on either side, a dozen, a score, each one a dark square mouth. The lamp lit perhaps twelve paces. Beyond that the dark lay thick as felt. And somewhere to the left, very far away, there was a sound he identified after a moment as the sea.

"Nana!" called Suzu.

The tunnel took the name and tossed it down the stone, Nana, Nana, Nana, thinner and thinner, until it was a thread, and then nothing.

"Do not shout at the same pitch," said Sael. "The vault resonates. Vary it."

She called again, lower. "Nana. Nana, it's Senpai."

They went on.

He took them left at the first fork, and left again, down a corridor so narrow that their shoulders brushed the walls, and the water rose to the shin. He did not hesitate. His feet knew it. He moved through the dark like a man walking through the rooms of a house he had lived in as a child, and the district unrolled under him, and he heard Suzu behind him, breathing quickly through her mouth.

They came to the arch on the nineteenth step.

He had known it would be there. That was what he told himself. It stood at the end of the corridor, set into the wall like a door that someone had once meant to open. It was a tall, narrow arch, built of old gray stone, and it had been filled in. Mortar, thick and pale, had been pressed into every gap, and stone blocks laid across the gap in neat courses. The mortar was a lighter color than the wall. It had been done much later. In the center of the arch, inlaid in the older stone, was a ring of tiles in a faded pearl glaze, wrought into a spiral that wound inward and inward on itself like a shell, or a wave, or a tide curve at its peak.

It was the gate. He knew it at once. It was the figure from the Office seal, the one on every writ and warrant, stamped in wax a hundred thousand times. But no one had ever told him it was a drawing of the gate itself. They had only told him it was a mark of authority.

"What is that?" said Suzu.

He had been standing very still. He realized it when she spoke. He realized, also, that he had been standing in that precise place, in exactly this posture, with exactly this angle of the lamp, before.

He remembered coming down the corridor. A small hand, his own, in a larger one. A voice saying, count them, Sael, count the steps with me. Nineteen. And then the arch.

And then nothing.

It was not darkness. It was not forgetting. He knew what forgetting felt like, in the abstract, from the way other people described it: the mist, the slow slippage. This was not that. This was a place in the column where the figure should have been, and there was no figure. The line ran from the arch to the stair, and in between was a blank the exact width of an afternoon. He reached for it, and his mind slid across it like a thumb across glass.

He had never in his life had a gap.

He felt his spine straighten. He had not intended it. He felt it go, one vertebra at a time, from the base to the crown, and he knew precisely what it meant, because she had told him, on a stair, in a voice like clear water. Stands up straighter when he lies.

"It is a sealed structure," said Sael. "It is of no relevance."

He did not look at her. He did not dare. But from the corner of his eye he saw her turn her head, and look at the arch, and then at him, and then at his shoulders. The pause went on for the length of a held breath. He heard the cap of her stylus click, once, and stop.

She said nothing.

She looked at the ring of pearl tiles for a moment longer. Then she turned her face away, deliberately, the way one turns from a door that is not one's own, and said in a very quiet voice, "All right. Which way?"

He could not have said what he felt. There was relief in it, and under the relief something sharp and shameful, because she had seen it, and she had let it be. She had seen the lie, and had weighed it against a girl in the dark, and had chosen the girl. It was the correct decision. It was what he would have done.

It was a measurement error, he told himself. A single dropped figure. It would resolve.

He did not believe it.

---

The corridor forked a hundred paces on, and they stopped.

"Left," said Sael.

"Right," said Suzu.

They said it at the same instant, and looked at each other, and the lamp hissed.

"The button was on the ladder," she said. "The current in the basin runs rightward. If anything fell, it would be carried right. If she lost something else, her slate, a lamp"

"She had no lamp."

"Then she'd feel for the wall, and the wall on the right is"

"The right fork floods first," said Sael. "It descends. It has no refuge niches. It terminates in a pump room that has been under water since before I was born. If she took it, she is no longer a matter for search."

There was a pause.

"The left fork," he went on, "climbs. It has three refuge niches above the high line. They were built for workmen. A child could reach them."

He watched her. He watched her face in the lamplight, the small hard lines at the corners of her mouth, the pulse in her throat. He knew what she was calculating. She had a sound argument. She was not wrong. The current did run rightward. He had simply a better one, and he was waiting, quite calmly, for her to take the whole thing apart and rebuild it, as she had done with the clauses of her guardianship, as she did with everything.

She did not.

She stood there, perhaps three seconds. Her hand went to her pocket, and found it empty, and came away. And then she lowered her chin, and said, in an odd, unsteady voice, "Left. Go left. I trust you."

It was the plainest sentence in the world. It went through him like a struck bell.

"You have no plan," he said, before he could stop himself.

"No." A short, breathless sort of laugh. "I have never done that before. It's terrible. Don't make me think about it."

He turned and went left, and she followed him up the slope, and he found that his hands, which were always so still, were not quite steady on the lamp.

---

They heard it in the second niche.

It was very faint. It was so faint that at first he thought it was the sea, the long sigh of the tide beyond the vault. But Suzu had stopped, dead, with one hand flung out against his arm, and he felt her whole body go taut, and she said, in a whisper like paper tearing, "Listen."

He listened.

"Se, npai?"

It came from far down the corridor, thin and cracked, torn into pieces by the stone. It was a child's voice. It was a child who had been calling for a long time, and had run out of breath, and was calling anyway.

"Nana!" Suzu was already moving. "Nana, we're here, we're coming, stay where you are"

"Do not run."

"Which way, which way is it"

"The third channel branch. East. It is the old drain." He caught her sleeve. "Arimura. Do not run. The floor is uneven. Follow."

She followed. She kept pace at his shoulder, breathing in short hard gasps, and he took them through two more turns without error, past a rusted grating, along a ledge that ran above a trough of black water. He had never been so aware of his own legs. The lamp swung and flared. The voice came again, nearer: thin, cracked, unmistakable.

And then, from somewhere behind and below them, there was a sound he had never heard in the under-wharf in all his years.

It began as a hum. A low, steady, grinding hum, like a mill-wheel under a floor, felt in the soles of the feet before it reached the ear. The surface of the water in the trough shivered. The lamp-flame leaned. In the dark behind them something large and slow began to move, and he felt the draft of it come up the corridor, cold and wet and smelling of the open sea.

"What is that?" said Suzu.

He stood quite still. He did the arithmetic. It took less than a second, and when it was finished he had the answer, and he did not wish to have it.

"The flood," he said.

"The sixth bell isn't for another"

"No," said Sael. "It is not."

The table was wrong. He had known the table was wrong by days. He had known it for six years, and had filed it, and had carried a small private resentment of the error ever since. And he had trusted, at the end, the one thing in the entire district that was never tested: that the sea would keep the Office's hours. It had not. The tide had come forty minutes early, on a full moon, with a swell behind it, and the third channel was already running full.

Water came round the corner.

It did not rush. It came the way a patient animal comes, in a long black muscular curve, curling along the floor and up the walls. It was at his shins before he moved. It was at his knees. He felt the cold grip him like a fist.

"Back!" Suzu was staring behind them, at the corridor they had come by, where the lamp showed nothing but a rising black mirror and the roof closing down to meet it. "Sael, the way back, it's going under"

"It is already under." He caught her wrist. It was the second time in his life he had done it, and the pulse in it was a small fast bird. "Up. There is a stair. Fourteen paces. Do not let go of me."

"Nana"

"I know."

"She's right there, she's right there"

"I know." He hauled her against the current, step by step, through water that dragged at every stride, and the lamp swung and the hum rose to a roar. "Arimura. Suzu. Listen to me. I will not let you drown. Climb."

She climbed.

Behind them, in the dark, the voice called again, faint and far, and then the water came up over the corridor with a long slow thunder, and the way back was gone.