Ninth Tower was built downward, and it took Suzu four flights of stairs to understand it.

The lower floors were gone. She saw that when Sael stopped on the third landing and lifted his lamp to the stairwell below, where the steps ran down into a black, perfectly still square of water and simply went on without them, each stair a little paler and wavier than the last, until the lamplight gave up. Somewhere down there, she supposed, were halls and kitchens and archive rooms, all of it drowned to the ceiling and patiently waiting.

"Do not go below the fourth step," said Sael. "The stone is slick and the water is colder than it appears."

"Is that a regulation?"

"It is an observation." He started up again. "I have been in the water. It is cold."

She climbed after him with his coat dragging around her knees. The lamp in his hand was a small sealed thing of green glass with a flame the size of a thumbnail, and it threw their shadows up the curve of the wall, his tall and straight, hers hunched and shapeless under the borrowed weight. The tower smelled of salt and wet limestone and, faintly, of ink. Every few steps there was a narrow window at waist height, and every window showed the same view: dark water, an enormous pale sky going to indigo, and the slow tolling of that distant bell.

"How many people live here?" she asked.

"One."

"In the whole tower?"

"Ninth Tower is a posting, not a residence. Auditors are assigned to a tower for the length of a gate cycle. Mine began eleven years ago. The gate has not opened in that time, so the posting has been, uneventful." He said the word the way a person tests a stair with one foot. "Until this evening."

"Eleven years of nothing and then five teenagers fall out of the sky."

"Statistically, it was inevitable. Sooner or later, a gate that is permitted to stand open will open."

"You said it wasn't permitted to open."

He was silent for two steps. "The gate is not permitted to open," Sael agreed. "That is not the same as saying it cannot."

She filed that away too. It was becoming a crowded shelf.

On the fourth landing he turned left along a corridor so narrow that she had to walk with her shoulder against the wall, and at the end of it he opened a door with a key he took from a ring at his belt. "The guest room," he said. "It is the only dry room on the lower half of the tower. I have not had occasion to use it."

It was small. A narrow bed with gray blankets folded square at its foot. A table, a stool, a shelf with nothing on it. A washbasin in the corner with a pitcher of water that did not smell of salt. A single window, shuttered, with a bar across the shutters that looked as though it had been oiled recently. The air was cool and very still, and when Sael set the lamp on the table the whole room seemed to lean toward it.

Suzu walked a slow circuit of the walls, touching things. She could not help it. The bed frame, the stool's three legs, the bar on the shutters. Her fingers went to her skirt pocket for the notebook and found damp cloth and nothing else, and she stopped in the middle of the floor with her hand flat against her hip.

"You are looking for something," said Sael from the doorway.

"No."

"You have reached for the same pocket eleven times since we left the landing."

She took her hand away. "It's a habit."

"You lost the object in the water." He considered her. "It has a function for you. It is not decorative."

"It was my notebook. It's where I keep, everything. The plan. The numbers. Who's supposed to be where." She heard how it sounded and lifted her chin. "I know how that sounds. But if I write it down, I don't have to be afraid I'll forget it."

"I do not forget."

"That must be nice for you."

The lid slid across his eyes and back. She was beginning to recognize it, the way you recognize a particular footfall in a house. He stood a moment longer, and then he did a thing she did not expect: he went out of the room, and she heard his step go away down the corridor, and a door open and close, and the step come back.

He held out a book.

It was a small, thick, squared-off thing, bound in pale waxed cloth the same color as the Auditor's ledger, with a blank first page and a sheaf of cream-colored leaves behind it. There was a stylus clipped to the spine. The pages smelled of fresh ink and clean stone.

"Outsiders may not keep a record of Kethari law," said Sael. "It is prohibited under clause eleven. The law is an Auditor's instrument, not a visitor's."

Suzu looked at the book in his hand. Then she looked at him.

"But," he went on, with no change of expression whatsoever, "outsiders are permitted a ledger of personal effects. It is a requisition item. It is used to inventory property and to prevent theft."

"Is that what this is?"

"It is an inventory book."

"An inventory of what?"

"Whatever you own."

"I own a school skirt and your coat," said Suzu.

"Then it will be a short book."

She made a small noise she did not intend, half a cough and half something else, and put her hand over her mouth. When she took it away, he was still holding out the book, perfectly grave, perfectly still, and one corner of his mouth had done something so slight she might have imagined it.

She took the book. It was heavier than it looked.

"Thank you," she said.

"It is a requisition," said Sael.

"I know. Thank you for the requisition."

He inclined his head, an exact quarter-inch, and she sat down on the stool and opened the first page. It was very white. She uncapped the stylus and held it above the paper, and for a moment she simply looked at the blankness, feeling the old order come up through her like warmth through cold hands. Then she wrote, at the top, in her small upright script: Terms.

"May I propose something?" she asked.

"You may propose anything. I may decline it."

"I would like to discuss the conditions of my guardianship." She did not look up. "Formally. I think it will be easier for both of us if we agree to the rules at the beginning, instead of finding out about them by accident."

There was a pause. "That is an unusual request."

"Is it prohibited?"

"No." She heard the stylus-scratch of his thumbnail against the doorframe. "I find that I do not object to it."

"Then I propose the following."

She set them out in order, numbering them as she went. One: that she be permitted to see her friends every day, at an hour to be agreed. Two: that she be informed of any decision affecting them before it was made, not after. Three: that she have free movement within the tower, excluding any room he designated private. Four: that he give her the reason for any restriction, in plain language. Five: that she be allowed to ask questions, and that he answer them or say that he could not.

Sael listened to all five with his hands behind his back. When she had finished he said, "One is acceptable. Eight o'clock each morning at the east quay, and not later than the second evening bell. Two is acceptable, with a qualification. I cannot inform you of decisions made above my rank before I am informed of them myself."

"Then tell me as soon as you know."

"Agreed. Three is acceptable. The private rooms are the third landing, the observation floor, and the chamber at the top of the stair. You will not need them." He paused. "Four, I would amend. 'Plain language' is a subjective term. I will give the reason. The language will be the best I can manage."

"That's fair."

"I am usually fair. It is a defect."

"Is it?"

"In this office, yes." Something in his tone slid sideways, almost unwillingly. "Five. I cannot always answer. I will say when I cannot."

"Then we're agreed."

"We are provisionally agreed. I have one condition of my own."

Suzu lifted her eyes. He had moved a half-step into the room, and the lamplight had caught the edge of his jaw and the slight, pearly sheen of his cheek. "Name it," she said.

"At the third bell tonight the tide will reach the lowest dry stair. It will push air up through the tower. You will hear it as a sound. It is the shape of a knock, but it is not a knock. You will not open the shutters, and you will not go to the stairwell. You will remain in this room until the fifth bell."

"Why?"

"Because the sound is very convincing." He said it plainly. "New arrivals have, historically, gone to the door."

"What happens to them?"

"Nothing. They wake the tower. It takes four hours to explain to the night warden. It is a significant inconvenience."

She waited for the rest of it, and he said nothing, and she realized that he really meant it was an inconvenience, and that the thing he was not saying was something else. She decided not to push. It was strange, to decide that. She wrote Condition 6 in the book and underlined it once.

"The third bell," she said. "Not the door, not the shutters. Stay in the room until the fifth. Understood."

"You will do it?"

"I said I would."

"People say that."

"Then watch me."

He watched her. It was a very odd feeling, to be watched by someone who would remember every second of it. Suzu bent her head to the book again, and under the table her free hand curled in the folds of his coat, and she heard, from the edge of the room, a soft, steady, quiet sound: tap, tap, tap, tap.

She looked up.

Sael was standing with one hand resting on the back of the stool, and the first two fingers of that hand were moving against the wood in an even rhythm. Not nervous. Not restless. Quite precise, like a pulse. He was not looking at his hand. He was looking at her page, at the list of numbered clauses, with an expression of grave and total attention.

She watched the fingers for a long moment.

He stopped.

"Is something wrong?" he said.

"No." She wrote a word she did not mean and crossed it out. "I was only thinking you're very easy to negotiate with."

"Most people find the opposite."

"Most people probably argue with you about the wrong things."

The fingers began again, quietly, tap tap tap, and this time neither of them mentioned it.

---

He left her at the fourth bell with a loaf of dense, dark bread, a bowl of something that tasted of seaweed and lemon, and instructions that she was to sleep. She did not sleep. She sat on the bed with the inventory book in her lap, writing and rewriting, until the stylus ran dry and she had to find the little reservoir in the spine and tip it open. She copied the five conditions neatly. She drew a box around Condition 6. She listed the people of her party and put a tick beside each name, and then, because the ticks did not feel like enough, she wrote the time of their last known location beside each one. Nana: east quay, 7:40. Ren: east quay, 7:40. It was the closest she could come to holding them.

Then the bell rang the third time, and the tower breathed.

She felt it before she heard it. A long, soft, internal pressure, like a held breath. The lamp flame leaned sideways. The shutters creaked once against their bar. And then, from somewhere far below her, came the sound.

Knock.

It was very quiet. It was exactly the sound of a knuckle on old wood.

Knock. Knock.

Suzu sat very still. She had been told it would happen, and she had still not been ready for how close it would sound. It did not come from the door. It came from the stairs. It came from the wall behind her bed. It came from somewhere low and near and patient, a sound with all the time in the world.

Knock. Knock. Knock.

"Suzu," said a voice.

Her whole body went cold.

It was Nana's voice. It was thin and breathless and exactly right, the small drawn-out vowel at the end of her name, the way she said Suzu as if it were two words. "Senpai. Senpai, I'm sorry, I couldn't find the quay. I'm at the bottom of the stairs. It's so cold. Please."

She was on her feet before she knew it. She had taken one step toward the door. Her hand was already reaching for the latch. The inventory book lay open on the bed where she had dropped it, and her own handwriting looked up at her from the page: Condition 6. Not the door. Not the shutters. The fifth bell.

She stopped with her fingers inches from the iron.

Nana was at the east quay. Nana was safe. She had written it down, she had counted her, she had seen her go into the boat and she had seen the boat go round the corner. Nana, 7:40, east quay. It was not a promise. It was data.

But it sounded like Nana.

"Senpai," said the voice, nearer. "Please. I'm scared. Why won't you come?"

Suzu pressed both palms flat against the wood of the door and rested her forehead against her hands. She did not open it. She did not say a word. She counted, deliberately, out loud, in a whisper, the names of the people she knew to be elsewhere. Haruto. Miyu. Ren. Nana. Haruto. Miyu. Ren. Nana.

The voice went on for what felt like an hour and was probably a minute. It begged. It wept. It asked her, in Haruto's cheerful drawl, why she had stopped counting. It said her own name in a dry, fond, ghostly tone that she did not recognize. And then the pressure in the tower eased, as slowly as a sigh, and the lamp flame stood upright again, and the knocking was only the settling of stone.

She let her breath out in a shudder. Her palms were wet. She had pressed so hard against the door that the print of the grain stood out in red on her skin.

The fifth bell had not yet rung. She sat back on the bed and waited for it, and counted the seconds, and when it finally rang she was still counting.

There was a soft rap at the door, an ordinary, human one. "Arimura," said Sael. "It is the fifth bell. May I enter?"

"Yes."

He opened the door and looked at her, and then looked at the door, and then at the red grain-mark on her palm. His face did not change. "You did not open it."

"No."

"It spoke to you."

"It sounded like Nana."

"It often sounds like what the listener most wishes to protect." He said it flatly, like a fact he had learned the hard way. "You were told. You complied. That is more than most."

"I almost didn't."

"Almost is a category I do not count."

There was something in it that was not quite coldness. She looked up at him, and found he was not looking at her but at the stool, the table, the bed with its smoothed gray blankets, as though assuring himself that every item was in its place.

"You believed me," he said. It was not a question. "About the tide."

"You hadn't given me any reason not to."

"You do not know me."

"No," said Suzu. "But you told me everything you were required to say, and one or two things you weren't. I've been trying to work out why."

"And?"

"I haven't worked it out yet."

He took a breath, the first she had seen him take that did not seem measured. "Nor have I," Sael said.

Then, as if he had said too much, he stepped back from the doorway. "There is a balcony on the fourth landing. The east quay can be seen from it, if the night is clear. You are permitted. It is not on the private list."

She went. She did not entirely know why. She took the coat with her, and the inventory book, and stood at the stone rail with her hair stirring in the warm wind, looking east.

The sea was a dark mirror. The sky was a vast, soft indigo scattered with stars that were wrong, all of them: wrong in number, wrong in color, a few of them very large and low and the color of old pearl. And across the black water, tiny and yellow and far, there was a row of lamps along a distant quay. She picked out the lodging house by its two upper windows. One of them was lit.

She raised her hand. It was a stupid thing to do. They could not possibly see her. She stood there with her arm in the air like a person hailing a ship, and she felt her throat go tight, and she did not put it down.

After a long time, the lit window flickered. Once. Twice. Three times.

Haruto, she thought. Of course. He would have found a way to signal. He would have talked someone into lending him a candle.

She laughed, a wet, shaky sound, and wiped her face with the back of her wrist.

She did not know how long she stood there. The balcony was cool and the tower was quiet and the sea made no sound at all. Somewhere behind her a door closed, and a step came very softly across the stone, and stopped.

"The tide is turning," said Sael. He had come to stand a few paces off, at the edge of the lamplight. He was in shirtsleeves, with his hands behind him. "You should sleep."

"I know."

"You will not."

"Probably not."

He did not leave. The wind moved in his dark hair. For a while they simply stood there, two silhouettes at a rail, with half a balcony between them. She could feel him thinking. It was the only way she could describe it.

"May I ask you a question?" said Sael. "It is not a regulation. It is a personal inquiry."

"Condition five. You're allowed."

He took a breath. "Between the water and the landing this evening, you counted your companions eleven times. I recorded each instance. Four is the stated minimum for a safety check; you said so to the one called Haruto, in the pool, I believe. Eleven exceeds it by a significant margin." His gaze did not leave the sea. "I have the number. I do not have the reason."

Suzu's hand tightened on the stone rail.

"Why do you count them," said Sael, very quietly, "as though one of them might be missing?"

The wind went through the balcony arches. Far across the water, a lamp in the east quay went out, and another, and the sky wheeled slowly overhead with all its wrong, beautiful stars.

She opened her mouth to answer, and found, to her astonishment, that she did not have a procedure for it.