Once again, Rizzoli gazed into the microscope and focused on a darker segment of the hair shaft. “The color’s not uniform,” she said.

“Go on.”

“There’s a black band on the shaft, a short way from the root. What is that?”

“It’s called distal root banding,” said Erin. “That’s where the sebaceous gland duct enters the follicle. Sebaceous gland secretions include enzymes that actually break down cells, in a sort of digestive process. It causes this swelling and dark band formation near the root end of the hair. That’s what I wanted you to see. The distal banding. It rules out any possibility this hair is your unsub’s. It may have been shed from his clothes. But not his head.”

“Why not?”

“Distal banding and brushlike root ends are both postmortem changes.”

Rizzoli’s head snapped up. She stared at Erin. “Postmortem?”

“That’s right. It came from a decomposing scalp. The changes in that strand are classic, and they’re pretty specific for the decomposition process. Unless your killer has risen from the grave, this hair could not have come from his head.”

It took a moment for Rizzoli to find her voice again. “How long would the person have to be dead? For the hair to show these changes?”

“Unfortunately, banding changes aren’t helpful in determining the postmortem interval. It could have been pulled from the deceased’s scalp anywhere from eight hours to several weeks after death. Hair from corpses embalmed years ago could also look like this.”

“What if you pull someone’s hair out while they’re still alive? Leave those hairs lying around for a while? Would the changes show up then?”

“No. These decompositional changes only appear while the hair remains in the dead victim’s scalp. They have to be plucked out later, after death.” Erin met Rizzoli’s stunned gaze. “Your unknown subject has had contact with a corpse. He picked up that hair on his clothes, then shed it onto the tape, while he was binding Dr. Yeager’s ankles.”

Rizzoli said, softly: “He has another victim.”

“That’s one possibility. I’d like to propose another.” Erin crossed to another countertop and returned with a small tray bearing a section of duct tape lying adhesive-side up. “This piece was peeled off Dr. Yeager’s wrists. I want to show it to you under UV. Hit that wall switch, will you?”

Rizzoli flipped the switch. In the sudden darkness, Erin’s small UV lamp glowed an eerie blue-green. It was a far less powerful light source than the Crimescope that Mick had used in the Yeager residence, but as its beam washed across the strip of tape, startling details were nonetheless revealed. Adhesive tape left behind at crime scenes can be a detective’s treasure trove. Fibers, hairs, fingerprints, even a criminal’s DNA left behind in skin cells, may adhere to tape. Under UV, Rizzoli could now see bits of dust and a few short hairs. And, along one edge of the tape, what looked like a very fine fringe of fibers.

“Do you see how these fibers at the extreme edge are continuous?” said Erin. “They run the whole length of the tape taken from his wrists, as well as from his ankles. They almost look like a manufacturer’s artifact.”

“But they’re not?”

“No, they’re not. If you lay a roll of tape on its side, the edges pick up traces of whatever the roll is lying on. These are fibers from that surface. Everywhere we go, we pick up traces of our environment. And we later leave behind those traces in other locations. So has your unsub.” Erin switched on the room lights and Rizzoli blinked in the sudden glare.

“What sort of fibers are these?”

“I’ll show you.” Erin removed the slide containing the strand of hair and replaced it with another slide. “Take a look through the teaching head. I’ll explain what we’re seeing.”

Rizzoli peered into the eyepiece and saw a dark fiber, curled into a C.

“This is from the edge of the duct tape,” said Erin. “I used forced hot air to peel apart all the various layers of the tape. These dark-blue fibers ran along the entire length. Now let me show you the cross section.” Erin reached for a file folder, from which she removed a photograph. “This is how it looks under the scanning electron microscope. See how the fiber has a delta shape? Like a little triangle. It’s manufactured this way to reduce dirt trapping. This delta shape is characteristic of carpet fibers.”

“So this is man-made material?”

“Right.”

“What about birefringence?” Rizzoli knew that when light passed through a synthetic fiber, it often came out polarized in two different planes, as though shining through a crystal. The double refraction was called birefringence. Each type of fiber had a characteristic index, which could be measured with a polarizing microscope.

“This particular blue fiber,” said Erin, “has a birefringence index of point zero six three.”

“Is that characteristic for something in particular?”

“Nylon six, six. Commonly used in carpets, because it’s resistant to stains, it’s resilient, and it’s tough. In particular, this fiber’s cross-sectional shape and infrared spectrograph match a DuPont product called Antron, used in carpet manufacture.”

“And it’s dark blue?” said Rizzoli. “That’s not a color most people would choose for a home. It sounds like auto carpet.”

Erin nodded. “In fact, this particular color, number eight-oh-two blue, has long been offered as a standard option in luxury-priced American cars. Cadillacs and Lincolns, for instance.”

Rizzoli immediately understood where this was going. She said, “Cadillac makes hearses.”

Erin smiled. “So does Lincoln.”

They were both thinking the same thing: The killer is someone who works with corpses.

Rizzoli considered all the people who might come into contact with the dead. The cop and the medical examiner who are called to the scene of an unattended death. The pathologist and his assistant. The embalmer and the funeral director. The restorer, who washes the hair and applies makeup, so the loved one is presentable for final viewing. The dead pass through a succession of living guardians, and traces of this passage might cling to any and all who have laid hands on the deceased.

She looked at Erin. “The missing woman. Gail Yeager…”

“What about her?”

“Her mother died last month.”

Joey Valentine was making the dead come alive.

Rizzoli and Korsak stood in the brightly lit prep room of the Whitney Funeral Home and Chapel and watched as Joey dug through his Graftobian makeup kit. Inside were tiny jars of cream highlighters and rouges and lipstick powders. It looked like any theatrical makeup kit, but these creams and rouges were meant to breathe life into the ashen skin of corpses. Elvis Presley’s velvet voice sang “Love Me Tender” on a boom box while Joey pressed modeling wax onto the corpse’s hands, plugging the various holes and incisions left by multiple I.V. catheters and arterial cut-downs.

“This was Mrs. Ober’s favorite music,” he said as he worked, glancing occasionally at the three snapshots clipped to the easel, which he’d set up beside the prep table. Rizzoli assumed they were images of Mrs. Ober, although the living woman who appeared in those photos bore little resemblance to the gray and wasted corpse on which Joey was now laboring.

“Son says she’s an Elvis freak,” said Joey. “Went to Graceland three times. He brought over that cassette, so I could play it while I do her makeup. I always try to play their favorite song or tune, you know. Helps me get a feeling for them. You learn a lot about someone just by what music they listen to.”

“What’s an Elvis fan supposed to look like?” asked Korsak.

“You know. Brighter lipstick. Bigger hair. Nothing like someone who listens to, say, Shostakovich.”

“So what music did Mrs. Hallowell listen to?”

“I don’t really remember.”