Sachs was now doing this, becoming someone else-the killer who'd engineered this terrible end to another human being.

Eyes scanning the scene, up and down, sideways: the cobblestones, the walls, the body, the iron weight…

I'm him… I'm him… What do I have in mind? Why did I want to kill these vics? Why in these ways? Why on the pier, why here?

But the cause of death was so unusual, the killer's mind so removed from hers, that she had no answers to these questions, not yet. She pulled on her headset. "Rhyme, you there?"

"And where else would I be?" he asked, sounding amused. "I've been waiting. Where are you? The second scene?"

"Yes."

"What are you seeing, Sachs?"

I'm him…

"Alleyway, Rhyme," she said into the stalk mike. "It's a cul-de-sac for deliveries. It doesn't go through. The vic's close to the street."

"How close?"

"Fifteen feet out of a hundred-foot alley."

"How'd he get there?"

"No sign of tread marks but he was definitely dragged to the place he was killed; there's salt and crud on the bottom of his jacket and pants."

"Are there doors near the body?"

"Yes. He's pretty much in front of one."

"Did he work in the building?"

"No. I've got his business cards. He's a freelance writer. His work address is the same as his apartment."

"He might've had a client there or in one of the other buildings."

"Lon's checking now."

"Good. The door that's closest? Would that've been someplace the perp could have waited for him?"

"Yeah," she replied.

"Have a guard open it up and I want you to search what's on the other side."

Lon Sellitto called from the perimeter of the scene, "No witnesses. Everybody's fucking blind. Oh, and deaf too…And there must be forty or fifty different offices in the buildings around the alley. If anybody knew him, it may take a while to find out."

Sachs relayed the criminalist's request to open the back door near the body.

"You got it." Sellitto headed off on this mission, blowing warming breath into his cupped hands.

Sachs videotaped and photographed the scene. She looked for and found no evidence of sexual activity involving the body or nearby. She then began walking the grid-walking over every square inch of the scene twice, looking for physical evidence. Unlike many crime scene professionals, Rhyme insisted on a single searcher-except in the case of mass disasters, of course-and Sachs always walked the grid alone.

But whoever'd committed the crime had been very careful not to leave anything obvious behind, except the note and the clock, the metal bar, the duct tape and rope.

She told him this.

"Not really in their nature to make it easy for us, is it, Sachs?"

His cheerful mood grated; he wasn't right next to a victim who'd died this fucking lousy death. She ignored the comment and continued working the scene: performing a basic processing of the corpse so it could be released to the medical examiner, collecting his effects, dusting for fingerprints and doing electrostatic prints of shoe treads, collecting trace with an adhesive roller, like the sort used for removing pet hairs.

It was likely that the perp had driven here, given the weight of the bar, but there were no tread marks. The center of the alley was covered with rock salt to melt the ice, and the grains prevented good contact with the cobblestones.

Then she squinted. "Rhyme, something odd here. Around the body, for probably three feet around it, there's something on the ground."

"What do you think it is?"

Sachs bent down and with a magnifier examined what seemed to be fine sand. She mentioned this to Rhyme.

"Was it for the ice?"

"No. It's only around him. And there's none anywhere else in the alley. They're using salt for the snow and ice." Then she stepped back. "But there's only a fine residue left. It's like…yes, Rhyme. He swept up. With a broom."

"Swept?"

"I can see the straw marks. It's like he scattered handfuls of sand on the scene and then swept it up… But maybe he didn't do it. There wasn't anything like this at the first scene, on the pier."

"Is there any sand on the victim or the bar?"

"I don't know… Wait, there is."

"So he did it after the killing," Rhyme said. "It's probably an obscuring agent."

Diligent perps would sometimes use a powdery or granular material of some kind-sand, kitty litter or even flour-to spread on the ground after committing a crime. They'd then sweep or vacuum up the material, taking most of the trace particles with it.

"But why?" Rhyme mused.

Sachs stared at the body, stared at the cobblestone alley.

I'm him…

Why would I sweep?

Perps often wipe fingerprints and take the obvious evidence with them but it's very rare when someone goes to the trouble of using an obscuring agent. She closed her eyes and, as hard as it was, pictured herself standing over the young man, who was struggling to keep the bar off his throat.

"Maybe he spilled something."

But Rhyme said, "Doesn't seem likely. He wouldn't be that careless."

She continued to think: I'm careful, sure. But why would I sweep?

I'm him…

"Why?" Rhyme whispered.

"He-"

"Not he," the criminalist corrected. "You're him, Sachs. Remember. You."

"I'm a perfectionist. I want to get rid of as much evidence as possible."

"True, but what you gain by sweeping up," Rhyme said, "you lose by staying on the scene longer. I think there has to be another reason."

Going deeper, feeling herself lifting the bar, putting the rope in the man's hands, staring down at his struggling face, his bulging eyes. I put the clock next to his head. It's ticking, ticking… I watch him die.

I leave no evidence, I sweep up…

"Think, Sachs. What's he up to?"

I'm him…

Then she blurted, "I'm coming back, Rhyme."

"What?"

"I'm coming back to the scene. I mean, he's coming back. That's why he swept up. Because he absolutely didn't want to leave anything that'd give us a description of him: no fibers, hairs, shoe prints, dirt in his soles. He's not afraid we'll use it to track him to his hidey-hole-he's too good to be leaving trace like that. No, he's afraid we'll find something that'll help us recognize him when he comes back."

"Okay, that could be it. Maybe he's a voyeur, likes to watch people die, likes to watch cops at work. Or maybe he wants to see who's hunting for him…so he can start a hunt of his own."

Sachs felt a trickle of fear down her back. She looked around her. There was, as usual, a small crowd of gawkers standing across the street. Was the killer among them, watching her right now?

Then Rhyme added, "Or maybe he's already been back. He came by earlier this morning to see that the vic was really dead. Which means-"

"That he might've left some evidence somewhere else, outside the scene. On the sidewalk, the street."

"Exactly."

Sachs slipped under the tape out of the designated crime scene and looked over the street. Then the sidewalk in front of the building. There she found a half dozen shoe prints in the snow. She had no way of knowing if any of them were the Watchmaker's but several-made by wide, waffle-stomper boots-suggested that somebody, a man probably, had stood in the mouth of the alley for a few minutes, shifting weight from foot to foot. She looked around and decided there was no reason for anybody to be standing there-no pay phones, mailboxes or windows were nearby.

"Got some unusual boot prints here in the mouth of the alley, by the curb on Cedar Street," she told Rhyme. "Large." She searched this area too, digging into a snowbank. "Got something else."

"What?"

"A gold metal money clip." Her fingers stinging from the cold through the latex gloves, she counted the cash inside. "It's got three hundred forty in new twenties. Right next to the boot prints."