"A lot of wild goose chases."

"That's right. A lot of them."

Betty continued to work. This stage of testing was relatively simple. She took the swabs from the test tubes I'd sent up to her, moistened them with water and smeared filter paper with them. Working in clusters, she first dripped naphthyl acid phosphate, and then added drops of fast-blue B salt, which caused the smear to pop up purple in a matter of seconds if seminal fluid was present.

I looked at the array of paper circles. Almost all of them were coming up purple.

"The bastard," I said.

"A lousy shot at that."

She began describing what I was seeing.

"These are the swabs from the back of her thighs," she said, pointing. "They came up immediately. The reaction wasn't quite as quick with the anal and vaginal swabs. But I'm not surprised. Her own body fluids would interfere with the tests. In addition, the oral swabs are positive."

"The bastard," I repeated quietly.

"But the ones you took of the esophagus are negative. Obviously, the most substantial residues of seminal fluid were left outside the body. Misfires, again. The pattern's almost identical to what I found with Brenda, Patty and Cecile."

Brenda was the first strangling, Patty the second, Cecile the third. I was startled by the note of familiarity in Betty's voice as she referred to the slain women. They had, in an odd way, become part of our family. We'd never met them in life and yet now we knew them well.

As Betty screwed the medicine dropper back inside its small brown bottle, I went to the microscope on a nearby counter, stared through the eyepiece and began moving the wetmount around on the stage. In the field of polarized light were several multicolored fibers, flat and ribbon-shaped with twists at irregular intervals. The fibers were neither animal hair nor man-made.

"These what I collected from the knife?" I almost didn't want to ask.

"Yes. They're cotton. Don't be thrown off by the pinks and greens and white you're seeing. Dyed fabrics are often made up of a combination of colors you can't detect with the naked eye."

The gown cut from Lori Petersen was cotton, a pale yellow cotton.

I adjusted the focus. "I don't suppose there's any chance they could be from a cotton rag paper, something like that. Lori apparently was using the knife as a letter opener."

"Not a chance, Kay. I've already looked at a sample of fibers from her gown. They're consistent with the fibers you collected from the knife blade."

That was expert-witness talk. Consistent this and reasonable that. Lori's gown was cut from her body with her husband's knife. Wait until Marino gets this lab report, I thought. Damn.

Betty was going on, "I can also tell you right off the fibers you're looking at aren't the same as some of the ones found on her body and on the frame of the window the police think the killer came through. Those are dark-black and navy blue with some red, a polyester-and-cotton blend."

The night I'd seen Matt Petersen he was wearing a white Izod shirt that I suspected was cotton and most certainly would not have contained black, red or navy blue fibers. He was also wearing jeans, and most denim jeans are cotton.

It was highly unlikely he left the fibers Betty just mentioned, unless he changed his clothes before the police arrived.

"Yeah, well, Petersen ain't stupid," I could hear Marino say. "Ever since Wayne Williams half the world knows fibers can be used to nail your ass."

I went out and followed the hallway to the end, turning left into the tool marks and firearms lab, with its countertops and tables cluttered with handguns, rifles, machetes, shotguns and Uzis, all tagged as evidence and waiting their day in court. Handgun and shotgun cartridges were scattered over desktops, and in a back corner was a galvanized steel tank filled with water and used for test fires. Floating placidly on the water's surface was a rubber duck.

Frank, a wiry white-haired man retired from the army's CID, was hunched over the comparison microscope. He relit his pipe when I came in and didn't tell me anything I wanted to hear.

There was nothing to be learned from the cut screen removed from Lori Petersen's window. The mesh was a synthetic, and therefore useless as far as tool marks or even the direction of the cut was concerned. We couldn't know if it had been cut from the inside or the outside of the house because plastic, unlike metal, doesn't bend.

The distinction would have been an important one, something I very much would have liked to know. If the screen was cut from the inside of the house, then all bets were off. It would mean the killer didn't break in but out of the Petersen house. It would mean, quite likely, Marino's suspicions of the husband were correct.

"All I can tell you," Frank said, puffing out swirls of aromatic smoke, "is it's a clean cut, made with something sharp like a razor or a knife."

"Possibly the same instrument used to cut her gown?"

He absently slipped off his glasses and began cleaning them with a handkerchief. "Something sharp was used to cut her gown but I can't tell you if it was the same thing used to cut the screen. I can't even give you a classification, Kay. Could be a stiletto. Could be a saber or a pair of scissors."

The severed electrical cords and survival knife told another story.

Based on a microscopic comparison, Frank had good reason to believe the cords had been cut with Matt Petersen's knife. The tool marks on the blade were consistent with those left on the severed ends of the cords. Marino, I dismally thought again. This bit of circumstantial evidence wouldn't amount to much had the survival knife been found out in the open and near the bed instead of hidden inside Matt Petersen's dresser drawer.

I was still envisioning my own scenario. The killer saw the knife on top of Lori's desk and decided to use it. But why did he hide it afterward? Also, if the knife was used to cut Lori's gown, and if it was also used to cut the electrical cords, then this changed the sequence of events as I had imagined them.

I'd assumed when the killer entered Lori's bedroom he had his own cutting instrument in hand, the knife or sharp instrument he used to cut the window screen. If so, then why didn't he cut her gown and the electrical cords with it? How is it he ended up with the survival knife? Did he instantly spot it on the desk when he entered her bedroom? He couldn't have. The desk was nowhere near the bed, and when he first came in, the bedroom was dark. He couldn't have seen the knife.

He couldn't have seen it until the lights were on, and by then Lori should have been subdued, the killer's knife at her throat. Why should the survival knife on the desk have mattered to him? It didn't make any sense.

Unless something interrupted him.

Unless something happened to disrupt and alter his ritual, unless an unexpected event occurred that caused him to change course.

Frank and I batted this around.

"This is assuming the killer's not her husband," Frank said.

"Yes. This is assuming the killer is a stranger to Lori. He has his pattern, his MO. But when he's with Lori, something catches him off guard."

"Something she does… "

"Or says," I replied, then proposed, "She may have said something that momentarily stalled him."

"Maybe."

He looked skeptical. "She may have stalled him long enough for him to see the knife on the desk, long enough for him to get the idea. But it's more likely, in my opinion, he found the knife on the desk earlier in the evening because he was already inside her house when she got home."