She brought him the plan on the third morning after the second squall, bound in a neat sheaf of grey paper and tied with a loop of white thread.

Caelan was in the map room, where he had been since the fourth bell, reading ward repair estimates he could not make himself believe. He heard her on the stair. Quick, even, nothing wasted. By now he could have picked her step out of a hundred. He told himself this was only a Warden's habit of knowing the tread of every person under his roof, and he did not examine the argument closely, because it would not have survived the attempt.

"Warden," said Sera, at the door.

"Stormbinder."

She crossed the room and laid the sheaf on the table in front of him, squared to its edge, and stepped back to exactly the distance protocol required. Her hair was pinned tight. The silver line on her left wrist showed faintly at the cuff. She had slept, he thought. Not much. But some. The violet under her eyes had faded a shade.

"A proposed schedule of range trials," she said. "For your review."

He untied the thread and turned the first page. It was beautiful work. He had expected competence, but this was something past it: columns ruled in fine black ink, paces down the left in intervals of ten, headings for onset, symptom, severity and recovery time, a separate table for observers. She had allowed for wind. She had allowed for the state of the tide, which had no bearing on anything he could think of, and then he saw the small note beneath it explaining that salt air might affect the conductivity of the bond, and he had to admit that he had not thought of that either.

"This is thorough," he said.

"I prefer to be."

"You propose to begin at fifty paces."

"And advance by ten. At each interval we hold position for one full minute and record symptoms independently. Then we close and compare."

"Independently."

"I would rather not have your account shaping mine."

It was a fair point. It was also, he suspected, an insult, though she had delivered it so evenly that he could not have said which part. He turned the page.

The last leaf of the sheaf was a summary table. Beneath the final row, in a smaller and less careful hand, she had written a line and then struck it through with a single hard stroke of the pen. He would not have seen it, except that the ink had bitten into the paper and left a faint furrow in the grain.

Threshold of severance (est.)

The question mark after it had been struck through as well.

He sat very still. A gull cried over the harbor. Somewhere below, a ward-keeper was hammering iron, steady as a pulse.

She was not mapping the bond. She was hunting for the place where it would break.

He understood it perfectly, and he found, with a kind of distant surprise, that he was not angry. He had been braced for anger. It was what he had earned, and what he would have felt in her position. Instead, something older and more tired settled in his chest, and with it a conviction as simple as a stone: that if there were a door out of this, she had every right to look for it, and that it would be better for her to look under his eye than to go looking alone.

"Fifty paces," he said. "Tamsin Hale stands by with her satchel. If either of us goes down, the trial ends. No arguments."

"Agreed."

"We stop at a hundred and ten. No further."

Her eyes flickered. "My count put the onset at one hundred and eleven."

"Then a hundred and ten is the last interval we will attempt." He tied the thread back around the sheaf. "I will not make you sick for the sake of a column in a table."

She looked at him for a long moment. Her face gave him nothing, but he saw her thumb move against the inside of her wrist.

"That is fine," said Sera.

It was not. He had learned that much. But he nodded, and she turned and left, and he sat with the grey sheaf under his palm until her footsteps had died away down the stair.

* * *

The harbor wall was nearly a quarter mile long, a pale, weathered spine of stone running out into the sea with an iron lamp post every thirty paces. Bram had strung a measuring cord along its length that morning and knotted a strip of tarred rag at every tenth pace, so that the whole wall looked as if it were wearing a row of small black flags.

Tamsin stood at the midpoint with her satchel on her hip and a look of enormous innocence. Bram sat on a bollard nearby with his arms crossed over his chest.

"I am not a witness," said Bram, before anyone could ask. "I am passing the time. It is a free wall."

"It is a Line wall," said Caelan.

"Then I am a Line officer, passing the time."

"Lieutenant."

"Warden."

Caelan gave up. There were battles worth fighting before breakfast, and this was not one of them.

Sera stood at the far end of the first fifty paces with her notebook open on one arm and a stub of pencil between her teeth. She looked, in the morning light, like a surveyor about to measure a field. She did not look at him.

"Begin," said Caelan.

It was nothing at fifty. A faint pressure behind the breastbone, no more, as though a hand had been laid there. He stood with his hands behind his back and counted sixty seconds and noted that the sea was calm and the sky was clear and the woman at the end of the cord was writing industriously and not looking at him in the slightest.

At seventy it was a dull ache, like the memory of a bruise. At ninety, a thin high ringing began at the back of his skull, and the lamp posts took on an odd, slow shimmer. He wrote on his slate: *tinnitus. Mild vertigo.* He looked up to see Sera frowning at the sea and rubbing one temple with two fingers, and without a word passing between them he knew that she had written the same thing.

They closed the distance each time and met in the middle, by the knotted rag, and compared their notes, and each time it was a small, stiff, careful skirmish.

"You wrote 'mild' for the vertigo," said Sera, at ninety.

"It was mild."

"You were listing to starboard."

"I was leaning into the wind."

"There was no wind."

"Then I was leaning into the absence of it." He looked at her notebook. "You have written 'moderate.'"

"It was moderate."

"You were gripping the lamp post."

"I was admiring the ironwork."

Behind them, Bram made a noise like a man sitting very hard on a laugh. Tamsin turned quickly and looked at the sea.

Caelan felt, absurdly, the corner of his own mouth twitch. He suppressed it. She saw him do it, and her eyes narrowed with suspicion, and her own lips went tight as though she, too, had something to suppress, and they stood there on the wall for one confused, bright second, each fighting down the same dreadful impulse.

Then she dropped her gaze to her notebook and said, in her flattest voice, "One hundred paces."

* * *

At a hundred, the world began to tilt.

It was a slow, sick, sideways slide, as though the wall were a deck and the sea beneath it had begun to swell. His ears roared. A cold sweat rose along his spine. He locked his knees and fixed his eyes on a lamp post and thought, with great clarity, *this is no trifling thing.* Down the long pale curve of the wall he saw the small figure at the far end sway and put out a hand to the iron, and straighten, and write.

He wrote on his slate: *Severe. Nausea. Loss of balance. Visual disturbance.* The letters wavered on the slate like weed in a current. When he looked up again, Sera was walking toward him with her chin high and her notebook clutched against her chest, and her face the color of tallow.

They met at the rag. She stopped an arm's length away. She was swaying, very slightly, and he knew without being told that he was doing the same.

"One hundred and ten," said Sera.

"That was the last interval."

"The last interval agreed."

He looked at her. Her eyes were too bright. There was a thin sheen of sweat at her hairline. "You will not like what I am about to say," he said.

"Then do not say it."

"We stop here."

"We have not yet reached the onset of collapse. My notes are incomplete."

"Valdis..."

"One hundred and ten gives us nothing we did not have from the wall on the first day." She spoke very fast and very low. "You know that. I know it. If we are to learn anything, we must go further, only by a few paces, only for a minute. Tamsin is here. The wall is dry. Please."

The word hung between them like a thing neither knew how to pick up.

He had heard her say a great many things in three weeks. He had not heard her say that.

He looked past her, along the wall, at the black rags fluttering in the wind, and saw Tamsin watching with a worried face and Bram on his bollard, no longer smiling. He thought of a sheaf of grey paper, and a line struck through, and the furrow the ink had left.

"A hundred and twenty," said Caelan. "I will go back to my mark. You will go to yours. We hold for thirty seconds. Not one more."

Something went across her face that he could not read. "Thank you," she said.

He walked back to his mark and turned and stood with his boots together and his hands behind him, and watched her walk away down the wall, small and straight and growing smaller, past the black rags at one hundred and ten, one hundred and fifteen.

He lost count after that. He could not have said afterward whether she walked ten paces beyond the mark or twenty. He knew only that when the bell in his chest changed its note, it did not clang or ring or toll. It simply stopped, and in the silence where it had been, the whole sky fell on him.

He saw her drop. A cut string, a fallen coat, a small dark shape folding down on the pale stone. He tried to shout. His mouth would not obey. The wall swung up and struck the side of his head, and he had time for a single clear and furious thought, *she went past the mark,* before the dark closed over.

* * *

He woke to a pale sky and the cry of a gull and the smell of salt and wet stone.

For a few moments he lay perfectly still and did not try to think. His head ached with a flat, dull, regular throb. His mouth tasted of metal. A coat had been folded under his skull for a pillow, and he knew by its weight that it was his own.

The bell in his chest was ringing again, low and steady and so near that it seemed to hum in the stones under his shoulder blades.

He turned his head.

She was lying beside him.

Not touching. Barely. Perhaps the width of a hand lay between his sleeve and her shoulder. Someone had carried her along the wall and laid her down on the dry stones with her coat tucked around her, and one arm had fallen outward in her sleep so that her fingers lay open on the rough pale ground a few inches from his own. Her hair had come out of its pins. It lay across the stone in a loose dark tangle, and a few strands of it had drifted across his sleeve.

Her face was turned toward him. Without the cool, careful set of her mouth it looked younger, and very tired. A smudge of soot lay along one cheekbone. She was breathing slowly, evenly, and every few breaths her lashes flickered, as if she were dreaming of something that required her to hurry.

He did not move.

It was not that he was weak. He was nearly sure he could have sat up. It was that some instinct, older than will, had taken hold of him and told him that if he stirred, the thing would end. The faint steady ring of the bond, the warmth at the edge of his sleeve, the small rise and fall of her breath. He would not be forgiven for any of it, and he did not ask to be. But for one minute, for two, he lay on a harbor wall under a washed sky and let himself have the exact sensation of not being alone.

He thought: *I should not be looking at her.*

He looked.

The silver line gleamed on her wrist where her sleeve had ridden up, faint as the track of a snail. Beside it, the little shell bracelet had slipped sideways, and one of the dull pink shells had caught a stray beam of light. He found himself, absurdly, counting them. Eleven. Elowen had threaded twelve. He had watched her do it, once, on a bench by the Harrow Coast seawall with her tongue between her teeth, saying that a dozen was lucky, that you couldn't lose with a dozen.

He shut his eyes.

The twelfth shell had been sewn to the hem of the cloak she wore on the night she did not come home.

* * *

He did not hear her wake. He felt it, in the way the bond's note shifted from deep to shallow, a change in the weather of the thing, and when he opened his eyes her eyes were open too.

Grey. Clear and cold and rain-colored. Very close.

Neither of them spoke.

The gull cried again. A rope creaked somewhere. The tide lapped at the foot of the wall. He watched awareness come into her face by degrees: the sky, the stone, the sleeve a hand's width from her shoulder, his face. He watched her find all three, one after another, and add them up.

She did not move. He thought she was possibly holding her breath.

"How far?" said Sera, at last. Her voice came out rough and low.

"A hundred and twenty."

"I did not feel it begin."

"It did not begin. It stopped." He kept his voice quiet. "You went ten paces past the mark."

"Yes."

"I said thirty seconds."

"I know what you said."

"You walked until I could no longer see which mark you stood on."

"I know." The corner of her mouth moved, not quite a smile, not quite a wince. "I needed to know."

"And now?"

"Now I know that a hundred and twenty paces drops us both like stones." Her gaze slid from his. "It is not a very useful finding."

"No."

"It was not worth it."

"No," said Caelan.

They lay there. The silence between them was neither the cold civil silence of the map room nor the brittle one of the cliff. It was something odder. Almost shy. A pair of animals who had woken in the same burrow and could not decide who ought to leave.

Then, with a stiff, deliberate motion, as though she were rising from a formal bow, Sera pushed herself up on one elbow, and sat, and drew her knees up, and moved herself exactly one pace away along the stone.

The bell in his chest dipped. Softened. He felt it, and did not say so.

"Thank you," said Sera, to the sea, "for stopping my head from hitting the wall."

"I did not. Tamsin did."

"Oh."

"I was already unconscious."

"Oh," said Sera again, and a very faint pink crept up the side of her throat.

* * *

Tamsin returned along the wall with a flask in one hand and two blankets over her arm, trailed by a pair of ward-keepers who had clearly been recruited for stretcher duty and were visibly disappointed to find both patients upright. She stopped a few yards off. She looked at Caelan. She looked at Sera. She looked at the one pace of empty stone between them, and the corners of her mouth began, very slowly, to rise.

"Good morning," said Tamsin.

"Tamsin," said Sera, warningly.

"No, no. I'm only observing. Clinically." She knelt, and held the flask under Sera's nose, and with the other hand, brisk and impersonal, took hold of her wrist and counted her pulse. "You went down like a felled tree. Both of you did. Bram carried the Warden to the lamp post, and Jory and Dace carried you to him, because the moment they set you down at a hundred and ten, you started to groan in your sleep." She released the wrist. "Pulse is fine. Pupils even. You'll live."

"I did not groan."

"You groaned. It was most affecting." Tamsin turned to Caelan with the flask. "Drink. Water and a little brandy. And now, since I have kept my side of the bargain and not let either of you die of science, may I ask a question?"

"If it is brief," said Caelan.

"Have you finished trying to murder each other?"

There was a pause.

"No," said Sera.

Caelan looked at her. She sat with her chin up and her hair in a wild dark cloud and a smear of soot on her cheek, and she looked, for the first time since she had arrived at Calder Port, entirely and uncomplicatedly like herself: stubborn, spent, unrepentant. He felt something in his chest give way, a small, warm, appalling thing, like ice cracking underfoot.

"Of course not," said Tamsin, and laughed, a short, helpless, wicked laugh that she smothered in her sleeve. "Of course you haven't. Bram, I owe you a week of night shifts. I was wrong. They are going to be at this until spring."

"I told you," said Bram, from a safe distance, with immense satisfaction.

Caelan drank the brandy and water. It burned all the way down. He did not look at Sera again, and he was aware, with every nerve, that she was not looking at him.

* * *

That night he sat at the map room table with the log open before him and the lamp turned low and wrote the entry he had written a hundred times, in a form he had never before found so difficult.

*Range trial, harbor wall. Cord of one hundred and twenty paces. Observers: Hale, Holloway, two ward-keepers. Onset of symptoms at fifty paces (mild). Moderate at ninety. Severe at one hundred. Collapse in both subjects at one hundred and twenty. Recovery on reapproach was immediate and complete.*

He stopped. He read it over. It was accurate. It was complete. It said nothing at all of what had happened.

He dipped the pen again.

*Subject Valdis exceeded the agreed limit by ten paces. Subject Thorne permitted it.*

He looked at the last line for a long time.

He had known precisely what he was doing. That was what he could not set aside. He had stood on the wall and watched her walk away, and he had weighed the thing, the agreement, the rule, the plain good sense of the matter, and he had let her go because she had said please. Not for the Line. Not for the bond. For her.

And when he had woken on the stones, in that first blind moment before thought, he had not asked himself whether the trial had succeeded. He had not asked about the range, or the data, or the Line. Before anything else in the whole wide world, he had turned his head to see whether she was breathing.

He had counted her breaths first. Then the Line.

It was a very small thing. He was a very disciplined man. He told himself so several times, with great firmness.

He drew a line beneath the entry and wrote one more sentence beneath it, in his plain, upright hand, and underlined it twice.

*Trials concluded. Not to be repeated.*

Then he laid down the pen, and took his father's badge from his coat, and turned it in the lamplight, thumb moving along the worn place on its rim, back and forth, back and forth. Three floors above him, a hundred paces off and no more, the faint steady bell rang its patient note.

He did not intend to listen. He listened until the lamp burned down.