Sid handed the mass spec report to Mac personally, a strange occurrence given he was hardly ever seen outside his morgue.

"Concrete dust; found in her nose, throat, and lungs. Most part of it cement – calcium silicates, aluminum oxide, iron oxide, the works."

"So we're looking for someone in the construction business."

"Or who lives near a building site. Unfortunately, that hardly narrows it down. Portland cement type one is found everywhere. Most buildings and houses would've had use of it."

Mac sat back, feeling a headache slowly creep up the base of his skull. His hand instinctively reached up.

"Anything else?"

"The cuts on her face? Some were consistent with blunt force trauma, but others were jagged, like those made by sharp rock edges. I found the same dust in those cuts and under her nails. Also, I've lifted off what turned out to be untreated petroleum jelly faintly streaked all over the body."

"Petroleum jelly?"

"All over the body."

Mac nodded his thanks and dismissal. A primary crime scene had been established, somewhat. He supposed that was a start.

- - - - - - - - - - - -

Mrs. Clarke was small next to her husband's 6-foot frame, almost vulnerable in her short curls and a smart collared dress. That was the initial impression formed after Mac and Lindsay knocked on their front door and were greeted by the couple.

"Mr. and Mrs. Clarke? We're from the New York Crime Scene Unit. Could we come in? It's about your daughter."

"Kathy?"

Mac noticed their intertwined hands turning white at the knuckles and his heart pushed painfully against his chest.

"Yes, sir."

They led them through into the hall. It was an elegant town house, simple and classic, nothing showy or extravagant; just rosewood panels and abstract art lining the hallways of the house.

"She's dead, isn't she?" Mrs. Clarke asked when they were all seated. It caught Lindsay off-guard.

"Ma'am?"

"I know she's dead. It's always like this," her attempted smile crumbled and tears slipped down her cheeks. "Isn't it, Albert? The police will come in and be all polite when they tell you and say nice things to make you feel better and-"

Her words were cut off when her husband pulled her into his arms, muffling her sobs. Mac and Lindsay shifted uncomfortably in their seats, feeling like intruders witnessing too private a moment.

"Is she? Dead, I mean, is that what you came to tell us?"

Mac slipped the photograph taken on the autopsy table from his coat jacket and handed it to the father.

"Is that your daughter, Mr. Clarke?"

The man held it, staring for a long minute before he crushed it and buried his face behind his fist.

- - - - - - - - - - - -

No DNA from the rape kit, nothing new from scrapings, no hair found on the vic's body, no blood on her that don't belong to her –

Danny glumly read over all the 'No's he had jotted down.

"I don't get it," he didn't look up when Mac entered, "How? I mean, he's like some ghost or something."

"He knows what he's doing. Guy this careful…"

"Must be a pro."

"A combination of skill, luck and rain, Danny. Did we get anything on what we bagged from the crime scene?"

Messer laughed weakly. "Loads of prints. Most of them belong to people whose worst crime was getting speeding tickets. Couple of juvvies: shoplifting and pick-pocketing charges to their names but not- hell, nothing of this sort."

He handed the list to Mac, who studied it, carefully hiding his disappointment when he too came up empty on potential leads.

"Wouldn't make sense anyway, Danny. He wouldn't be this careless."

"Figures. So, what now, boss?"

"We keep at it. Her parents should be here soon to give their statement. Tell me if anything unusual shows up in Trace."

- - - - - - - - - - - - -

"You'd think it was Times Square, what with the amount of human print traffic we're getting off these plaster casts."

Danny peered over as Adam laid out the castings.

"This one's at least three prints deep," he grumbled lightly, prodding at a mould with the tip of his caliper, "you can hardly make out the individual print patterns."

"Got anything for me?"

"Far as I can tell, seven different people were around that rock, and other than that of the witness lady, all other prints were made before it rained, that much I can say."

Danny held up the cast nearest to him and ran a finger over the overlapping ridges, frowning when he noticed something odd.

"Where was this from?"

Adam checked his notes. "Somewhere equidistant from the road and the body."

"This here's a print over a print. You see how random this one is," he picked up another for comparison, "but here, this guy placed his foot exactly over the other. A size 11 this one, but I can't tell who it belongs to."

"I'll check through the others, see if there's any matching print for this." He strained his eyes and muttered a 'Damn' when he realized the wet mud had shifted and blurred the ridges, leaving him with indistinct prints. Danny saw the problem as well.

"Alright, see if you can extricate the top print from the one below on this, Adam. The rain's gone and messed it up good."

"Will do."

- - - - - - - - - - -

Mac scanned through the same four files late into the night. The seeming lack of evidence was frustrating him more than usual and his headache was back with a vengeance. He sipped at his cup of coffee, grimacing when he tasted the cold flat liquid.

It was half an hour into midnight when his mobile buzzed at his hip. He flipped it open and CallerID read Flack's name on the screen.

"Yeah."

"We've got another one, Mac. I think we could be looking at a serial."

TBC