He motioned, and I peered through the eyepiece and had no trouble identifying what had drawn his interest, jagged-edged, translucent flecks adhering near the lower edge of the letter. After examining the newspaper clip and the envelope, he again turned the microscope over to me. On both, easily identifiable, was what appeared to be an identical residue.

Saying nothing, Nguyen, who had the manner of an irritated Pomeranian when he was hot on the trail of a bone, collected a microscopic sample of the substance from the lower right-hand corner of the sheet of paper, followed by examples from the news clip and envelope.

"Lets test its IR," he said, with a broad grin. Nguyen held a palpable esteem for his infrared microscope. Although it resembles any other microscope, the IR has one big difference: instead of lenses, it relies on mirrors that reflect a specimens infrared energy, so it can be charted and identified.

Readying the sample, he focused in on the material through clear gla.s.s optical windows. Nguyen then swung the windows out of the way and lined up a series of curved mirrors. During the process, infrared energy pa.s.sed through the microscope into the sample, where the mirrors redirected the energy to sensitive detectors, resulting in a chart of peaks and valleys, resembling an electrocardiogram of a heartbeat.

"What is it?" I asked when hed finished, prompting him to look at me as if I were the specimen under his microscope.

"Havent the foggiest," he said, plainly irritated. "Give me a minute."

With that, Nguyen keyed in a command and the IR microscope transmitted its results to a computer designed to compare the readout to a library of known patterns. The results came quickly.

"Its a polycarbonate," he said.

"You mean a plastic?" I asked. "What kind? Plastics leave dust?"

"Plastic resins do," he explained. "In a raw stage, like the plastic pellets used in manufacturing."

"So, what does this tell me?" I asked, eager for anything that could break the case out of its current slump. "Tell me how we can capitalize on this to find this guy before he tortures and kills someone else."

"Im not sure," Nguyen admitted, looking uneasy. I suspected that, isolated in the lab, he rarely thought of the bigger picture, the ramifications of his work. To him, that dust was merely a specimen to a.n.a.lyze. To me, it was a clue to the ident.i.ty of a killer who had already butchered four people, including the mother of four young children.

"If this is a generic plastic resin, it may not help at all," he admitted reluctantly. "But if its a more specialized compound..."

"How do we find that out?"

"Ill work on the samples and run a few more tests. Well also send the envelope in to start having it checked for DNA, in case our guy was dumb enough to lick it shut," he said. "Ill let you know as soon as I have any answers."

Two hours later-after Nguyen tapped the FBI lab for a.s.sistance-I was on my way to the Harkins Plastics Company in southeast Houston, an unimpressive compound of three vast metal buildings on a dead-end street in a neighborhood populated by blue-collar families with roof-top satellite dishes and chain-link fences. Nguyen and his counterparts at the FBI had discovered not only a UV stabilizer in the plastic resin, added to keep the clear material from discoloring when exposed to light, but an antibacterial additive so new it was still under patent to a Ma.s.sachusetts chemical corporation. One call to the main office in Boston and I discovered that Harkins was the only company in Texas using resin containing the additive.

As I waited in the lobby for the owner, Theodore Harkins, I examined a dusty display case. Next to trophies won by the company Softball team sat heavy, bright yellow-and-red plastic pipe fittings, probably built to specification for one of Houstons many oil companies. I bent down to get a better look. My eye was drawn to a spiral of clear plastic tubing on the bottom shelf.

"Thats our medical line," said Harkins, whod walked up behind me. "Thats what we discussed on the telephone, the product were building with the new additive."

I followed Harkins, a slope-shouldered, thick-necked man with curly hair and a wide mustache, to the main conference room. One complete wall held shelves of product guides from plastic resin manufacturers. The sign outside boasted that Harkins had been family-owned for sixty-five years. From the look of this room, theyd done little to update. Dusty and worn, the thin green carpet buckled in places under our feet. The Formica-topped conference table bore the scars of decades of use.

"Im not really sure how we can help you," Harkins said, with a wary smile. "Yes, we use that type of plastic in manufacturing, but all our employees have been here for years. Were a family business, and I trust all of them."

"Can you show me where the tubing is made?" I asked.

Harkins nodded and turned, and I followed. Through the door at the rear of the room we entered a storage area. We were surrounded by large bins of pea-size plastic pellets-white, black, some bright red, yellow, and blue.

"Thats the resin, the way it comes in to be used in manufacturing," he said. "All different types of polymers specialized for individual jobs."

"Which one has the additive?" I asked. He indicated containers near the back of the room, and I walked over and picked up a milky-white pellet, rubbed my thumb over it, and a powdery residue came off.

"Its an exciting new product," Harkins said. "Perfect for medical usage."

The clanking of heavy metal machinery reverberated off the walls as we walked through a second set of doors and snaked through the factory, past two rows of ma.s.sive steel machines attached to computers, each monitored by a silent worker. Through a window in one of the machines, I watched as liquid plastic was drawn into a mold and expelled into dies which cast it into tube-like branches, of the sort that hold together the pieces of a model airplane. This time, however, each branch ended in a one-inch cube. A stooped, gray-haired woman sat, patiently cutting the boxes from their plastic stems, tr.i.m.m.i.n.g off the excess with a tool similar to a wire cutter and then methodically a.s.sembling two cubes to form small white plastic boxes.

"Postage stamp containers," Harkins explained. "We have a regular contract. But come this way. What you want to see is back here."

After pa.s.sing workers piecing together a specialized toothbrush for dentures, Harkins and I left the building for a smaller structure bordering the parking lot. Inside, a dozen sparkling new machines churned. In contrast to the rest of the plant, this building was meticulously clean and well lighted. Focusing so intently on their work that they failed to acknowledge our presence were six white-smocked workers, one middle-aged black woman, three Hispanic men, and two Anglos, one man and one woman. The first four didnt fit the San Antonio description. Of the two Caucasians, the woman appeared in her fifties with salt-and-pepper gray hair. The man caught my full attention. He was young, slender, with chin-length blond hair. From the side, I examined his profile. Could he? Could he be the killer? I felt for my pistol under my jacket and slipped my hand around the grip.

"These machines extrude the resin into the tubing using three hundred and sixty metric tons of hydraulic force," Harkins said, picking up a yard-long spiral of the clear plastic tubing. "We got the contract about two years ago. Its a component for a new dialysis machine. The antibacterial qualities of the plastic..."

In the background, I heard Harkins drone on about the plastic and the additives promise for the future, princ.i.p.ally in medical applications. I couldnt take my eyes off the young man with the blond hair, who bent over a carton filled with more yard-long sections of the finished tubing, expertly maneuvering a long thin-bladed knife to trim any imperfections on the cut ends. He was the right height, the right coloring. The curve of his face resembled the outline of the composite, and I began to ease my gun out from under my jacket.

He must have felt my eyes boring into him, for he suddenly looked up and returned my gaze. Full-face, his bone structure was wrong, as were his eyes, a dark, dark brown. But something else convinced me this wasnt our killer; the man had a half-dollar-size birthmark the color of red wine across his right cheek. Lily Salas would not have missed that in her ID.

The man smiled at me and I smiled back, gingerly taking my hand off my pistol in the holster.

"Who else has access to this room?"

"Just the cleaning staff," Harkins said.

"Id like to see your employee records."

In the privacy of his office, I took out a copy of the San Antonio composite.

"No one I know," said Harkins.

"Youre sure?" I asked, and Harkins nodded. "If you dont mind, Id still like to take a look at your files."

Since the company had a small contract for a component for NASA, plastic hinges used in the shuttle galleys, all of Harkinss employees had a base-level security clearance, including file photos and fingerprinting. After a quick look-see, I left the plant carrying copies of the files on all the companys employees-including the cleaning staff-for the past two years, the length of time theyd used resin containing the antibacterial additive. None resembled our guy, but I couldnt take chances; I had to be sure. If the letter hadnt been exposed to the resin there, then where?

At the office, later that afternoon, Id just handed the files to Sheila to give to Nguyen to start on the fingerprints, when the captain cornered me.

"You got another one. Todays mail," he said. "Its in the lab."

Nguyen already had the letter under the microscope when the captain and I walked in.

"Anything?" Captain Williams asked.

"Nothing," he said. "Same as before, a few prints on the envelope and nothing on the letter. Nothing remarkable about the paper itself. Its standard copier paper, just like the last letter. No debris except what appears to be traces of common dirt."

"Let me see it," I said.

Wearing latex gloves, Nguyen inserted the letter and envelope-postmarked Sat.u.r.day from a Dallas zip code-in evidence sleeves then gave them to me.

Some are chosen to live, others to die.

This is destiny.

The hand that wrote it was the same as the first, and I had no doubt he was our killer. He was warning me, but at the same time taunting me with his power. His murders gave him control over the lives and deaths of his victims. Now, the killer believed he could control the police, the investigation. He believed he could control me.

"Sarah, we need to talk," the captain said, and from the tone of his voice I knew he wasnt about to compliment my investigative techniques. This was bad news. "We just cant have this. This has gone too far. This guys fixating on you. Im sure, when you look back on this, youll agree. I really have no choice other than to remove you from this case."

The captains words. .h.i.t me full force. One thing I was sure of-I would not be replaced. If for no other reason than me with the letters, the killer had made this personal. For my own safety, so I could sleep at night, I had to make sure he was found and put away, forever.

"Im making progress, I can find this guy. I know I can," I protested. "Im your best hope and, until this creep is stopped, hes going to keep killing."

"I dont doubt that. None of us do. But its too dangerous; theres just too much risk for you, personally, to continue on," he said.

Maybe the captain was right. But in my heart, I felt certain I was the best person to stop this nightmare. "Bringing someone new on now, itll take days for them to get up to speed. In the meantime, this guys out killing people," I argued.

"I know that," the captain shot back. "But this guys focusing on you. We cant take any chances that may put you in jeopardy. If youre not worried about yourself, think of Maggie and your mother. If he cant get to you and he figures out how to get to them..."

My stomach tightened into a ball at the thought that the killer could go after Maggie and Mom. But I knew that couldnt happen. "How would he find them? Theyre safe on the ranch. The place has nothing to do with me. None of the property records, the utilities, not the phone, nothing out there is in my name. Its all in Moms name. On paper, I havent existed since Bill died. My cars t.i.tled to the department, and even my cell phone is state-issue. My mail comes to the office and a post office box. This guy can run a complete computer search on me and not find an address or a telephone number that links me to the ranch, Maggie, or Mom."

"Youre sure?"

"Im sure," I said.

"No, I still dont..." the captain began.

"Three days, seventy-two hours," I countered. "Give me three days, and if I havent made an arrest, I wont argue. If you still want to, you can take me off the case. I wont fight it."

"Its not your performance. Its for your own good, your safety."

"Mom and Maggie are safe at the ranch, and I can take care of myself," I said, meaning it. "Three days, Captain Williams. Thats all Im asking for, just three more days."

The captain didnt appear to know exactly what to do. "Youll be careful?"

"Yes. Ill be careful."

"All right," he conceded. "But keep a low profile. A very low profile."

"Agreed," I said, relieved but wondering if I could live up to my part of the bargain. My latest clue had just proven yet another dead end. The evidence was mounting, but it led precisely nowhere.

"Three days," I repeated. "Then, if I havent made an arrest, I wont argue."

At ten that evening, I was in the office conference room reviewing evidence, rereading the two letters, searching for any overlooked clues, feeling overwhelmed and exhausted when David walked in.

"Thought Id find you here," he said. "I heard about the letters."

"I know the answer to all this is here somewhere right in front of me. It has to be. Why cant I see it?"

"Youre tired, Sarah. Its been a long day," he said, in a tender voice I felt certain he reserved for those he deemed to be precariously balanced. "Lets get a drink and then both go home."

In Davids car, we drove to a nearby Tex-Mex restaurant and claimed two stools at the bar. I chewed on chips with queso and green sauce. My first margarita went down quickly and I ordered another. Silent, David lingered over his scotch and soda. I knew he was doing the same thing I was, rethinking each piece of evidence, wondering what we were missing, why we didnt have the answers we needed. Halfway through my second drink, I just wanted to go home.

"Im sorry, Im not very good company tonight," I admitted.

"This was a bad idea," he agreed. "Were both too wrung out for this to help."

He stood up.

"Come on, Ill take you back to the office for your car."

The drive took only minutes. In the parking lot, he pulled into the slot next to my Tahoe and waited. I hesitated. I suddenly didnt want to leave. The truth was, at that precise moment, I wanted more than anything not to be alone. If Id been honest, I would have admitted I was both frightened and lonely. If Bill had been waiting for me, Id have had him to talk to. He would have found a way to make it all go away, at least for tonight.

David made no move to suggest he thought I should leave. Before I even realized what I was doing, Id turned toward him and lightly skimmed his cheek with the back of my hand.

"Five oclock shadow," I said, smiling. "Long day."

"Very long," he agreed, taking my hand in his.

This time I made no move to pull it away as he gently turned my hand over and kissed my open palm.

"Am I overstepping?"

"No, youre not," I said, edging forward, feeling a bit like a bashful adolescent with a new boyfriend. I ran my other hand through his tousled hair. "There, Ive been wanting to do that," I said, smoothing it back.

"You didnt need to ask," he said, bending toward me. "You could have done that the first day we met."

Our lips met full and hard, and I felt his hands beneath my blazer, pulling me toward him.

We said nothing as he drove out of the parking lot toward his house. There, in his bed, surrounded by his photographs, his books, we made love. We came in a rush of pent-up anxiety. For those brief moments, I felt the ache of the past year dissolving. In the morning, I knew, the world would be as I had left it, full of loss and frustration, but for just a little while, nothing existed outside that room and the feel of his firm naked body pressed against mine.

"I told you this before, the first time you came to this house with me, and I meant it. I have wanted you ever since I first saw you," he said, nuzzling the side of my neck, his breath warm and moist.

"I think I knew that," I said, lifting his face toward me and running my mouth over his. He tasted of scotch and me. "I think maybe I felt the same way."

David gently skimmed his hands over my bare b.r.e.a.s.t.s and fondled my nipples. My body quivered, and I pulled him closer, until he rolled on top and pressed hard against me. Wanting him even closer, I wrapped my bare legs around the small of his back and pulled him tight. This I had missed, the feel of a mans body, hard and firm.

His tongue caressed my neck and ear, searching for my lips. David arched his back, and my body relaxed and tensed. For a moment, the past was the past and nothing existed outside the walls of Davids bedroom, not grief or anxiety or guilt. Nothing but the feel of his body and the sparks it ignited within mine. My legs tight around him, I rolled onto my side, taking him with me and pushed him down onto the bed.

"My turn," I said, and David chuckled.

"Have your way with me," he whispered.

"Ah, just the way I like a man," I said.

I ran my hands over his solid muscles, his thick arms. I climbed on top of him, and he bent his knees and brought up his legs behind me, and once again I felt my body respond.

"Oh," I whispered. "David, I..."

"We can talk later," he said, grabbing my neck and pulling me toward him. The kiss was long and slow, and I hoped it might never end.

At that precise moment, on the nightstand his cell phone rang.

David caught it before the second ring. I didnt feel rejected. I would have done the same. Ten minutes later, we were dressed and on our way to the airport, where the captain had arranged to have a DPS helicopter waiting.