The body came in at seven on Monday morning, wrapped in a blue plastic tarp and dripping saltwater onto the lab floor.

Elias heard the gurney before he saw it. It rattled down the long corridor with a hard, hollow rhythm, and the transport men talked in low voices as they brought it through the double doors. They had the look of men who had been up since four and had already seen enough. One of them, a thick-necked fellow named Dobbs, shook his head as he steered the trolley to table two.

"Dockside," he said. "Pier Nine, out by the service road. Night watchman found him at ten to five. Hit and run." He wiped his palm on his trouser leg. "I've seen a few. This one's a mess."

"Name?"

"Joe Kowalski. Forty-seven. Longshoreman, been on the docks twenty years. Wallet was in his pocket." Dobbs hesitated. "There was a picture in it. A little girl. His kid, I guess."

Elias nodded. He did not ask to see it.

They lifted the tarp. Underneath lay a man of middle height, thick through the chest and shoulders, with a broad weathered face and a gray stubble of beard. He wore a heavy canvas work jacket, a hooded sweatshirt, steel-toed boots. His hands were large and scarred. A knitted cap lay crushed beneath his head, the yarn stiff with something dark.

It was a hard sight, and Elias took it in without comment, as he took in all of them. He signed the transfer. He thanked the men. When they had gone, he stood for a while at the foot of the table with his gloved hands folded, and looked at the face.

"I am sorry," he said, quietly. "I will do it properly."

He worked for three hours.

Nothing about the examination was easy. The injuries were severe, and they overlapped, and the first hour went to sorting one from another. A broken pelvis. A fractured spine. Both femurs shattered, and six ribs on the left, and a skull that had struck something hard. He photographed each wound, and measured each, and wrote the figures on his pad in a small cramped hand. It was only when he came to the chest that he stopped.

He stood very still, with the tape in his hand.

On the front of the canvas jacket, across the ribs, ran a broad flat band of crushed fabric. It was a foot wide. It ran from the left shoulder to the right hip, and in the middle of it, pressed deep into the weave, lay the pattern of a tire tread. He had seen such things before. A heavy vehicle had passed over this man's body, wheels first, and left its signature in the cloth.

But that was not what held him.

It was the second band.

It lay across the first, at a slightly different angle, a few inches lower, and it was fainter. A second pass. The same tire, a little to the right of the first track, running the other way. He knelt and examined it under the lamp, tracing the direction of the nap with the tip of a probe. The first impression had been made going forward. The second had been made in reverse.

He sat back on his heels.

It was a very quiet thing to see. There was no blood on it, no gore, nothing to make a person turn away. A few smears of grease and a faint print on a coat. But Elias looked at the two tracks, side by side, and felt the cold go through him from the base of his skull to his hands.

A driver who strikes a man in the dark may be a coward, or a drunk, or a fool. He strikes, and panics, and drives on. That was an accident, in the eyes of the law, and a terrible one.

A driver who strikes a man, and stops, and reverses over him again, has made a decision.

He photographed it from four angles. He measured the spacing between the tracks, and the angle of the offset, and the width of the tread. Then he rose, and took off his gloves, and washed his hands for the full three minutes, and sat down at his desk to write.

The paint came next.

It lay in a small smear on the hem of the jacket, a thin bright crescent no longer than a thumbnail, and he found it only because the light caught it as he turned the garment over. A flake of enamel, white at the surface, with a faint ring of blue beneath. A transfer from a bumper, or the lip of a fender. He lifted it with a pair of forceps, and set it in an evidence envelope, and sealed it with his initials.

"It is white over blue," he said. "Industrial. Two coats. The blue is a primer, I think, a marine grade."

"Marine." Quinn was bent over his shoulder with a magnifier in her hand. She had arrived a little after ten, in her leather jacket and a scarf the color of cranberries, with her hair pinned up carelessly and her eyes bright. She did not stand in the doorway, now. She came in as she came into every room, forward, looking at everything. "So a boat. Or something that works around boats."

"A truck, more likely. A heavy one."

"A work truck." She let out a long breath. "Okay. I can run that. The lab's got a database of commercial fleet paint. Every manufacturer files their formula." She grinned at him. "It'll take a day. Maybe two."

It took four hours.

She came back to the basement at half past two with a sheet of paper in her fist and an expression of such fierce and simple satisfaction that Elias, who was labeling specimens at the bench, lowered the jar.

"Got it," she said.

"Tell me."

"It's a custom blend. White enamel over a blue marine primer. Nobody uses it but one outfit in the whole state." She slapped the paper down on the bench. "Kestrel Marine Contracting. They do the dockyards, the piers, the heavy construction on the waterfront. All their fleet vehicles are painted that exact scheme. White and blue, with a little gold K on the door."

"Kestrel."

"You know them?"

"I have seen the name."

He had. He had seen it on a sign, on a morning in October, on the wire fence that ringed the foundation of a half-finished tower on the south harbor. He had seen it stenciled on the side of a yellow crane. KESTREL MARINE. Brandt Wharf Residences. He had stood in the gray dawn, with the tide coming in, and looked at that name, and not thought about it again.

"They're the biggest marine contractor in the city," said Quinn. "They've got the contracts for the whole Waterfront Trust redevelopment. The wharf, the piers, the new bridge approaches. Seventy employees, maybe a hundred trucks." She was pacing now, with a quick restless stride, her hands in her jacket pockets. "And you know who's on their board of advisors? Guess."

"I could not."

"Edmund Aldridge. The Senator. He's been on it for years." She stopped. "He doesn't take a fee. It's honorary. But his campaign fund gets a very nice donation from Kestrel every quarter, and his old chief of staff is their vice president for government affairs."

He said nothing.

"It's probably nothing," Quinn said. "It's a big company. Everyone on the waterfront has some link or other. But it's something to hang a hat on, you know?" She looked at him, and her face was flushed and eager. "I mean, it's a lead. It's the first lead we've had on anything in a month."

"It is a lead."

"I'm going to tell the captain."

"Yes."

She went out. He stood alone at the bench with a jar in his hand and the heavy chill of the lab pressing in around him. He did not move. He was thinking of a smile in a golden room, and a hand held out, and a name that had hung in the air between them like a drop of oil on water.

He was thinking: it is not nothing.

He told himself that it might be. A hundred trucks. A thousand men. A coincidence of paint and politics. But he had seen the face of a man at the end of a row, and he had seen another man standing behind him, quite still, with eyes that did not blink. And he could not help it. He watched the door.

He saw Luke at six o'clock.

It was in the apartment, in the kitchen, at the oak table. Elias had come home early, and had made the tea himself, a small private act of defiance, and had been sitting for ten minutes with his hands around the cup when the front door opened and a quick light step crossed the hall.

Luke came in with a bag of groceries in one arm and a stack of folders in the other. His coat was dark with rain. His face was pale, and there were fine tired lines at the corners of his eyes, but he smiled when he saw Elias, a quick open pleased smile, and set the bag on the counter.

"You have made tea," he said.

"I am capable of it."

"I never doubted it." He shed the coat. "Quinn found me at the office. She was so excited that she forgot to lower her voice, and half the floor heard. She says you found a paint chip."

"It was a small one."

"It was an extraordinary one." He crossed to the table, and laid the folders on the wood, and sat down opposite. His eyes were warm. "I do not know how you do it. A few grains of enamel, and a man's whole night is told."

"It is not mystical. It is a matter of looking."

"Yes. I have said so before." He opened the top folder. "I thought that I would read the Kestrel file this evening, if you do not object. Quinn has sent it over. I wished to have it by me when I speak to her in the morning."

"I do not object."

"Thank you."

He bent his head over the pages.

Elias drank his tea. He did it slowly, watching over the rim of the cup. It was a quiet, ordinary scene, the sort of thing that goes on in a thousand kitchens: a man at a table with his sleeves rolled, a pen in one hand, a folder spread out under a lamp. The refrigerator hummed. The rain ticked on the glass.

He told himself that he was not watching. He watched.

Luke read slowly.

That was the first thing. It was not a skimming sort of reading, the quick sweep of a tired officer scanning a report. He went through each page line by line, with his finger moving down the margin, and he paused at certain places and went back. He turned one page and then turned it back again. He took up the pen, and made a mark, a small neat tick in the margin beside a name, and then went on.

Fifteen minutes passed. Twenty.

The folder was a thick one. It held a corporate history, a list of officers, a schedule of contracts, three years of financial statements. It held a photograph, in the front, of a heavy gray-haired man in a hard hat, standing on a quay with his arms crossed, and a caption that read CALVIN DUNNE, FOUNDER AND PRESIDENT. And Elias saw, as the page turned, the way the pen moved when it reached that name.

It stopped.

It hovered above the paper, quite still, and the hand that held it did not move at all. Then, slowly, with a care that was almost tender, it drew a circle around the name. A single red circle, small and exact. Then another circle, inside the first. Then a line, drawn out to the margin, and at the end of it, in the square black hand that Elias had seen on a thousand forms, a note.

He could not read it. He was too far away. But he saw that it consisted of two words, and that the second of them began with an A.

He put down his cup.

It was not a loud sound. But Luke's head came up, and the pen paused, and for a moment they looked at each other across the lamplit table with the file between them. The air in the kitchen seemed to tighten. Luke's face was composed. His eyes were clear and mild and faintly inquiring, and nothing in them gave anything away.

"Is something wrong?" he asked.

"You are reading very carefully."

"It is a large file."

"It is a hit-and-run."

"Yes." A pause. "It is also the first lead in a month."

"You have circled a name."

"I circle a great many names." The corner of his mouth moved. "It is a bad habit. I did it as a boy, in schoolbooks. My mother used to scold me."

Elias said nothing.

He sat very still, with his hands flat on the wood, and looked at the man across the table. He looked at the slight bend of the neck, and the lamplight on the dark hair, and the pen held easily in the scarred hand. He thought of a pier at midnight. He thought of a stage, and a podium, and a smile like a lamp turned up.

"Is this your case?" he said. "Or is it the next link?"

It was out before he could stop it.

He heard it fall into the room. It lay on the table between them like a dropped glass. The rain ticked at the window. The refrigerator hummed. And Luke, who had been about to turn a page, stopped, and set down the pen.

He did it slowly. He laid it parallel to the edge of the folder, quite straight. Then he folded his hands on the open page, and lifted his eyes, and the look that came into them was not one that Elias had seen before.

It was a look of such plain, unarmed honesty that it hurt.

"This is Joe Kowalski's case," said Luke.

His voice was low and quite steady.

"He was forty-seven years old. He had a daughter who is eleven. She has a school play on Friday, and she will not have a father in the audience. A man hit him with a truck, in the dark, on a service road, and stopped, and drove over him a second time. You told me that yourself. You found it. You were the only person who would have." He drew a slow breath. "Joe Kowalski deserves to know who did it. He deserves a name, and a trial, and a sentence, whoever has been sitting behind it. I will give him that. I will give it to him if I have to carry the whole of Kestrel Marine into court on my back."

Elias held very still.

"I am not hiding behind this case," Luke went on. "I would like you to know that. I would not do it to him. I would not do it to you." His eyes held steady. "I will not pretend that I am indifferent to the name that I circled. I do not think you would believe me. But I will tell you that if the man who sent that truck is guilty of what I think he is guilty of, I will see him in the dock before I see him anywhere else."

He stopped. His hands, folded on the page, were white across the knuckles.

"Is that sufficient?"

It was.

That was the dreadful thing. Elias sat with his own hands on the table, and could not find a word to set against it. He had come in with a hard small cold suspicion, and it had dissolved in the face of that plain gaze like frost on a window. He had looked into the man's eyes, and he had seen nothing at all but truth.

He was telling the truth. Elias knew it, as he knew his own name. Luke wanted justice for a longshoreman he had never met, and wanted it with the whole of a deep and honest heart.

And he wanted something else, too.

The two things lay in him side by side, plain and undisguised. He wanted justice for Joe Kowalski. And he wanted Calvin Dunne, for reasons that had nothing to do with a service road. Elias could not tell which of them weighed more. He thought, perhaps, that Luke could not either.

"Yes," he said, at last. "It is sufficient."

"Thank you."

"I should not have asked."

"I am glad that you did." The faint tired smile returned. "I would rather be asked than watched."

He took up the pen again.

Elias rose, and carried his cup to the sink, and rinsed it. His hands were not quite steady. He stood for a moment with the water running over the china and his back to the room, and then he turned off the tap and went to bed.

But he did not sleep. He lay awake for a long time, listening to the low steady scratch of a pen in the kitchen, and thought about a circle drawn twice in red.

Quinn rang at nine the next morning.

He took the call in the lab, at his desk, with the receiver pressed to his ear and one hand on the file he had been writing. Her voice was quick and breathless and a little tight, and she was speaking from what sounded like a stairwell.

"I talked to the foreman at Kestrel," she said. "A guy named Burke. Big, red-faced, very polite. Showed me the whole yard. The trucks, the logs, the dispatch book. I asked him whether any of his vehicles had been out near Pier Nine at four-fifty on Monday morning."

"What did he say?"

"He said no. Flat. He said none of the crew works that shift, and the yard's locked from eleven to five, and the gate has a camera." Her breath came out in a rush. "And I believed him, Dr. Mercer. I really did. He had the log right there. Every vehicle signed in and signed out. Every key on a numbered hook. There's no way anyone took a truck."

"But."

"But." Her voice dropped. "I asked to see the GPS records. They put trackers on all the heavy trucks. Insurance. And the guy got this look, you know, just for a second, and then he said sure, no problem. He pulled it up on a screen. It's a map, with little dots. And I went through the whole night."

Elias waited.

"Truck twenty-two," said Quinn. "A white Ford, ten-ton, with a flatbed. It's in the yard at eleven. It's in the yard at midnight. At four-thirty in the morning, the dot just stops. The tracker goes dark. Nothing. No signal. It stays dark for forty-five minutes." A pause. "At five-fifteen it comes back on, right where it was. In the yard. Parked. Like nothing happened."

The lab was very quiet.

"Somebody switched it off," said Elias slowly.

"Somebody who knew how. It's a little box under the dash. You pull one fuse." She swallowed. "I asked Burke about it. He said it was a glitch. He said the units cut out all the time. He said he'd have the techs look at it." Her voice cracked. "He was sweating, Dr. Mercer. It was forty degrees in that yard, and he was sweating through his shirt."

"Who drives truck twenty-two?"

"That's the thing. Nobody. It's a spare. It doesn't have an assigned driver. Anyone with a key could take it, and every key was supposedly on a hook." She stopped. "I asked who had access. He said anybody on the day crew. That's sixty guys."

"Sixty."

"Sixty-two. I counted." She laughed, a short breathless sound without any mirth. "I could interview them all. It'd take a month. And every one of them is going to say the same thing, because somebody told them what to say." A silence. When she spoke again, her voice was small and flat. "I don't know how to find him. I don't know who was in that truck."

He looked at the file under his hand.

It lay open on the blotter. A man's name at the top, a case number, a list of injuries. A photograph, which he had not been able to look at for long, of a broad kind face under a knitted cap. Below it, in his own cramped writing, a line: second pass, reverse. Intentional.

He thought of a longshoreman, forty-seven years old, walking along a service road in the dark. He thought of a pair of headlights. He thought of a man in a cab, and a foot on a pedal, and the second of stillness when he might have gotten out.

There was a way to know who he was. There was only one.

He knew it already. He had known it since Monday morning, when the tarp was drawn back, and he saw the bruise on the chest where the tire had crossed. It had not been a decision. It had been a quiet cold certainty, like a stone settling to the bottom of a pond. He had sat through the whole of a day and a night, with a hundred small things to do, and in the back of his mind the stone had gone on sinking.

It had been fourteen days since the last.

Fourteen days. He could count them. Fourteen days since a woman on a stairwell, and a heavy warm arm in the dark. It was the longest he had gone since the first week of October. His body, he thought, was perhaps strong enough.

Perhaps.

"Dr. Mercer?" said Quinn. "Are you still there?"

"I am here."

"Do you have any ideas?"

He looked at the photograph.

"I will let you know," he said.

He set down the receiver. He sat for a long time without moving. The hum of the ventilation seemed to grow louder in the empty lab, and the light from the lamp lay in a small green circle on the paper, and somewhere in the corner of the room the refrigeration units drew in their long slow breath and let it go.

It would not be pleasant. He knew that. He knew exactly how it would be.

But there was a girl of eleven, with a school play on Friday.

He stood. He crossed the room. He took his white coat from its hook, and slipped his arms into it, and smoothed the cuffs of his gloves with his thumb, from the center outward, once to the left and once to the right.

Then he went to the cold room and drew out the drawer, and stood for a long time looking down at the broad weathered face.

Not yet, he told himself. Tonight. When the building was empty, and the preparations had been made.