Elias returned the coat the next day.

He did not do it in person. He had it cleaned at a dry cleaner on Ferry Street, pressed and folded and wrapped in brown paper, and he left it on the chair behind Captain Harrow's desk at seven in the morning, before the day shift arrived. There was no note. He had written and discarded six of them, each one more stilted than the last, and in the end had decided that the fewer words there were, the fewer ways they could be misread. It was only afterward, walking back down the stairwell with his hands in his pockets, that he realized the dry cleaner had scrubbed every trace of rain and cedar out of the wool. He felt a small stab of loss so foolish that he refused to name it.

Harrow said nothing about the coat when they met at the loading dock at half past five the following morning. He said, "Good morning, Doctor," and opened the passenger door of an unmarked gray sedan, and Elias got in.

The drive to the waterfront took twenty-five minutes, and neither of them spoke for any of it.

It was not an uncomfortable silence. That was what Elias found strange. He had spent his life in the company of people who filled quiet with noise, the way a person fills a hole with earth, and he had learned to hate it. Harrow simply drove. He kept both hands on the wheel, and his eyes on the wet road, and the windshield wipers made a slow, patient rhythm that seemed to keep time with the drizzle. The heater ticked. The radio was off. The sky ahead was the color of dishwater, and the streetlights along the harbor road were beginning to go out one by one.

Elias sat with his hands folded in his lap and his kit case between his boots. He kept his gaze on the window. He was intensely aware of the man beside him: of the width of his shoulders, the faint scent of soap, the quiet economy of his movements. He was aware of the space between them, about eighteen inches of gray upholstery, and of how carefully it was being preserved.

Ahead of them, through the mist, the harbor came into view.

Blackwood's waterfront had once been a working port, all cranes and rusting warehouses and the smell of diesel. Now half of it was being converted into what the billboards called waterfront living, glass towers and boutique restaurants and gated marinas. The Brandt Wharf Residences stood at the southern end, an unfinished skeleton of concrete and steel rising from a rubble-strewn lot at the water's edge. Yellow tape fluttered around the perimeter. A single patrol car sat near the gate with its engine idling.

"Victim four," Harrow said, and parked. "Gerald Brandt. Found on the thirtieth, in the foundation pit on the seaward side. You have seen the file."

"I have read it eleven times."

"Then you know what I know."

"No," Elias said. "I know what the file says. I want to see what it does not."

Harrow glanced at him, and there was a flicker of something that might have been approval. "That is why I brought you."

They signed in with the officer at the gate and ducked under the tape. The site was quiet in the gray dawn, the great machines idle, the scaffolding dripping. The ground was a churned mess of clay and gravel, and Elias picked his way across it carefully, his kit case in one hand. The air smelled of salt and diesel and wet concrete. Somewhere beyond the half-finished walls, he could hear the slap and hush of water against stone, and the thin, crying voices of gulls.

He stopped at the edge of the foundation pit, where the police had left a small square of yellow marker.

"Here," said Harrow, coming up beside him. "He was found on his back at the bottom, dressed in his evening clothes. Throat cut. The numeral four on his chest."

"Time of death?"

"Between one and two in the morning."

Elias nodded slowly. He did not look at the pit. He opened his kit case and took out a folded sheet of paper, and held it out to the captain, who took it and unfolded it.

It was a table. Columns of figures in a careful, cramped hand, with times along the left margin and heights along the top.

"Tide table for the harbor," Elias said. "The night of September twenty-ninth into the thirtieth. I overlaid it against the site plan this week, when I could not sleep."

"You have not slept in some time."

"Not the point." He pointed with one gloved finger. "This site is bounded on three sides by concrete, and on the fourth by the harbor. The only ground-level access from the water side is a maintenance ramp running under the pier, here. At high tide it is submerged to about four feet. At low tide it is dry. I checked the tables. On the night Brandt died, the ramp was exposed for exactly forty minutes, between ten past one and ten to two."

Harrow was silent, studying the paper.

"The police assumed the killer came in by road," Elias went on. "The security guard was sent home at midnight with a stomach complaint, the gate was unlocked, no forced entry. Everyone assumed someone with keys. But the road access is lit and visible from three sides. The ramp is not. If you wanted to move a body onto this site without being seen, you would use the water. And you would have exactly forty minutes."

"He timed it to the tide."

"He timed it to the tide." Elias looked out across the churning gray of the harbor. "He knew the schedule, and he built the murder around it. That is not opportunism. That is planning."

Harrow lowered the paper. For a moment he stood with his eyes on the water, his expression unreadable. When he spoke, his voice was quiet.

"Show me the ramp."

They went down through the rubble toward the seawall. Harrow walked ahead, and Elias followed a pace behind, watching the captain's back. He moved across the broken ground with a kind of loose, unhurried certainty, stepping over rebar and pooled water without looking down. When they reached the top of the ramp, he stopped and turned in a slow half-circle, taking in the pier and the pit and the concrete pillars and the long empty sweep of the yard.

"He came in here," Harrow said. He gestured at the water. "A small boat. Flat-bottomed, shallow draft, no motor, or a very quiet one. He would have put in at the marina to the south, half a mile down. There is a public launch, no cameras. He would have waited under the pier until the ramp cleared."

"You are certain?"

"No." Harrow's mouth quirked. "But it is what I would do."

He walked down the ramp, and Elias followed, and Harrow's voice went on in that low, even tone, describing the killer's movements as though he were narrating something he had watched. Here he tied off. Here he stepped ashore, on the left, because the right side was mud. Here he waited, in the shadow of that pillar, where the light from the road did not reach. He would have been able to see the whole site from here. He would have watched Brandt arrive in his car, and get out, and stand looking at the pit with his hands in his pockets, thinking whatever a man like that thinks when he is alone with his own money.

"He would have let him stand there for a minute," Harrow said softly. "Long enough to think he had arrived at something. And then he would have stepped out."

Elias had stopped walking.

There was something in the way Harrow said it. Not the words, which were plain enough, but the ease. The fluency. It was the voice of a man reciting a route he had walked many times. A very good detective could reconstruct a crime from a few marks in the mud and a table of tides. Elias had read dozens of profiles by exactly such men. But there was a difference between imagining a scene and remembering it, and Elias could feel that difference like a stone in his shoe.

He examined the thought for a moment, and then, deliberately, put it down.

Harrow was the best investigator in the department. It was his job to think like the man he hunted. That was all. It was only the exhaustion, and the strangeness of the last few days, that made every sentence sound like a confession.

"You are good at this," he said.

Harrow glanced back at him. He looked, for the first time that morning, faintly embarrassed. "I have been at it a long time."

"You describe it as though you had been here."

"I have been to many places like it." The captain's voice was mild. "It is the job."

He turned back toward the water. Elias followed him.

The clouds had grown heavier while they talked. The gray of the sky had deepened to slate, and the wind from the harbor had picked up, cold and briny. At the foot of the ramp the water lapped at the concrete in small, quick slaps. A moment ago it had been ten feet away. Elias frowned. He looked at his watch, and then at the water, and then at the tide table he had folded into his pocket.

"That is wrong," he said.

"What is?"

"It should not be rising yet. Not for another two hours." He pointed. "There was a storm surge. The rain last night. The runoff is pushing the harbor up." He crouched and touched the edge of the ramp with a gloved finger. It came away wet. "The ramp is going under."

Harrow was already moving. He looked back the way they had come, up the long concrete slope to the rubble yard, and Elias saw his expression change as he saw what Elias had seen: a dark line of water spreading across the lowest stretch of the ramp, thin and quick as spilled ink, cutting them off from the yard.

"We can go back by the seawall," said Harrow. "There is a ledge that runs along the base. It is narrow, but it is dry. It will bring us out at the north gate."

"How narrow?"

"About fourteen inches." He hesitated. "There is a railing."

Elias looked at the ledge. It ran along the base of the seawall, a thin gray lip of concrete with a rusted iron rail on the waterward side and a wall of wet stone on the other. Beneath it, the harbor churned, dark and green and clotted with weed. It looked like the kind of path a man walks only when he has no choice.

"I do not like heights," he said, which was not true. He did not like water, and he did not like edges, and above all he did not like having nowhere to put his hands.

"I will go first," said Harrow. "You will follow. You need not look down."

"I am not afraid of falling."

"No?" Harrow's eyes met his, quiet and steady. "Then what?"

Elias did not answer.

They went single file. Harrow led, his back to the wall, moving crabwise along the ledge with one hand on the rail. Elias came after, a pace behind, his kit case clutched to his chest with his left arm and his right hand gripping the rail so hard that he could feel the rust bite through three layers of leather. The wind tore at his coat. Spray whipped up from below and stung his face. The ledge was slick, and the rail was cold, and the stone at his back was rough and dripping.

He kept his eyes on Harrow's shoulders. The dark line of them moved ahead of him through the mist, steady and unhurried, and for some reason that was the thing that kept his feet moving.

They were perhaps forty feet along when the ledge narrowed.

It happened without warning. A section of concrete had crumbled away, leaving a jagged bite out of the ledge, and the rail beside it hung loose from its mounting. Harrow stepped across it easily and turned to wait. Elias set his boot on the wet edge.

It slid.

It was only an inch or two. But his weight was already committed, and the kit case swung out from his chest and dragged him sideways, and his right foot went out from under him. He grabbed for the rail. His gloved hand closed on cold iron, and held, and the world lurched, and below him the harbor opened up gray and hungry and impossibly close.

And Harrow's hand came down on the rail, right beside his.

He did not reach for Elias. He did not grab or catch or steady. He simply set his hand on the iron an inch from Elias's own, palm down, bare, broad, scarred at the knuckles, and Elias saw it with the sudden vivid clarity of a man who is half falling: the veins along the back, the faint white line of an old cut across one finger, the warmth rising off the skin into the cold air.

An inch. Less.

Elias wrenched his hand away as if the iron had turned red-hot.

It was a terrible mistake. His weight was on the loosened boot, and taking his hand off the rail was the one thing he could not afford to do, and for one long endless second he was falling backward into the wind with nothing beneath him but air. His stomach dropped. His kit case flew from his arm and struck the water with a flat slap. He heard himself make a sound, short and raw.

Then his left hand hit the wall behind him, and found a crack in the stone, and gripped.

He hung there. His heart hammered. His right boot found the ledge again, and he pressed himself back against the wet stone with his eyes squeezed shut, and breathed.

"Doctor."

The voice was very close, and very calm.

"I am right here."

Elias opened his eyes.

Harrow had not moved. He stood with his back against the wall, one foot on either side of the broken place, his bare hand still resting on the rail where Elias's had been. He had not reached for him. He had not so much as leaned in. But his face was tight, and there was a paleness under his tan that had not been there a moment before, and his eyes were fixed on Elias with an intensity that made the air feel thin.

"I am right here," he said again, more quietly. "I will not touch you. I have not. If you need me to, I will. That is up to you. But I am not going anywhere."

The wind howled. The harbor slapped at the stone below. Elias's chest heaved.

He had never in his life been so grateful for being left alone. And he had never, either, wanted so badly for someone to take his hand.

The thought went through him like a cold blade. He shoved it down. He pressed his back against the wall and gripped the crack in the stone until his knuckles ached.

"Go on," he said, and his voice was rough. "Walk ahead. I will follow."

"Doctor..."

"I said I will follow."

Harrow looked at him for another long moment. Then he nodded once and turned, and stepped carefully onto the far side of the break, and began to move along the ledge. He went slowly. He kept his hand on the rail. And every few steps, without turning his head, he said something low and steady into the wind. A little farther. You are doing well. Watch the third stone, it is loose. He did not look back, and he did not stop.

Elias followed him.

It took eleven minutes to reach the end of the ledge. He counted them. At the end there was a set of concrete steps leading up to a small platform, and a rusted mooring cleat bolted into the stone, and beyond it a low gate that opened onto the north end of the yard. Elias climbed the steps on legs like water and sat down heavily on the top one. His kit was gone. He was soaked to the knee. His hands would not stop shaking.

He looked at them. He was ashamed of that. He turned them over slowly, and then, because he could not stop himself, he looked at the mooring cleat.

There was a length of cord tied around it.

It was a short piece, no more than a foot, of thin white nylon line, frayed at one end where it had been cut with a blade. It had been looped twice around the neck of the cleat and secured with a knot. It was such a small thing, so ordinary among the barnacles and rust that Elias would have looked straight past it if he had not spent his entire adult life training himself not to.

He looked at the knot.

He leaned closer. His breath slowed.

It was a square knot, in the beginning. Right over left, left over right. But the first turn had been given a second throw, a doubled twist that locked it flat, and the ends had been trimmed off short and square. It was the sort of knot that did not slip and did not loosen. It was neat. It was quick. It was the kind of knot he himself tied a dozen times a day, in the sutures that closed the bodies on his table.

A surgeon's knot.

"Captain," he said, and his voice was hoarse. "Come and look at this."

Harrow came up the steps and crouched beside him, and Elias pointed without touching. The captain looked. He was silent for a very long time.

"It was not there on the thirtieth," Elias said. "Or it was, and no one saw it. But it has been tied here since. The cord is clean. The knot is a surgeon's knot. Double throw on the first turn. You would learn it in your first year of residency, or from a very good book." He swallowed. "He cleaned everything. Every print, every hair, every thread. But he could not clean his hands. This is what his hands do when he is not thinking."

"So he ties like a surgeon."

"Or like someone who learned from one."

"Or someone who studied very carefully."

Their eyes met. Harrow's were dark and calm and quite unreadable. He did not blink. For a moment neither of them said anything, and the wind pulled at their collars, and gulls wheeled screaming overhead.

Then Harrow said, "Photograph it. Do not touch it. I will call the evidence team."

Elias took out his phone and photographed the knot from four angles. His hands were still trembling, but he steadied the phone against the stone. He did not think about what he had just said, or what it might mean. He did not think about the pale scarred hand that had settled on the rail beside his own. He photographed the knot and stored the pictures and let himself simply be cold and wet and alive on a concrete step in the gray morning, until the shaking eased.

They walked back to the car in silence.

The tide had turned again by the time they reached the north gate. The sky was lightening. A thin bar of pale gold showed along the eastern horizon, where the clouds were beginning to break. Harrow opened the trunk of the sedan and took out a battered steel thermos, and unscrewed the cap, and poured something into the lid. Steam rose from it, fragrant and dark.

He did not hand it to Elias.

He set it on the hood of the car, a good six feet from where Elias stood, and stepped back two paces, and turned his face toward the harbor as though he found something there of great interest.

Elias looked at the cup.

It sat on the gray metal, steaming, alone. It was a small thing. It was nothing. But he stood there for a long moment with his soaked coat clinging to his legs and his hands hanging at his sides, and he understood, with a faint and terrible clarity, that he was being given a choice. Not the cup, but the space around it. The distance. The permission to take it, or not, without anyone watching him do it.

He walked over. He picked up the cup in both gloved hands.

It was tea. Black, hot, unsweetened. He took a sip. The heat ran down his throat and into his chest like a slow bright river. It was the first thing anyone had handed him in years, and he had taken it without a word, and Harrow, standing at the water's edge with his back turned, did not look around.

Elias drank the tea slowly. The harbor stretched out before them, gray and gold, and far across the water the land rose in a long dark ridge above the fog. He let his eyes travel along it, idly, the way one does. The old ferry landing. The cluster of derelict warehouses. The shoulder of the hill.

And on the crest of it, black and jagged against the paling sky, the shell of a burned house.

His hand stopped halfway to his mouth.

It had been twelve years. He knew every line of it. He knew the way the roof had fallen inward, and the chimney that still stood alone like a broken tooth. He knew which window had been his mother's. He had trained himself for a dozen years never to look at that ridge, never to drive that road, never to stand on this shore at dawn when the fog was thin. And here he was, holding a cup of tea, looking directly at it, and the cup was rattling against his teeth.

He turned away so fast that the tea slopped over his glove.

He kept his back to the water. He stared very hard at the side of the sedan, at the wet dull paint, at a single drop rolling down the window, and he breathed. In. Out. In. He did not look at Harrow. He did not want to see whether the captain had noticed. He could feel his pulse in his throat, hammering.

He did not see Harrow look around.

But when he finally dared to lift his eyes, some minutes later, the captain was standing at the edge of the wharf with his hands in his pockets, gazing across the harbor at the far ridge. He was very still. His face, in profile, was calm, and closed, and utterly without expression. He stood as a man might stand at a graveside, and for a long time he did not move.

"We should go," Harrow said at last. His voice was quiet. He did not turn his head. "You are cold, and the evidence team will be here soon."

"Yes," said Elias.

Neither of them looked at the ridge again.