“I’m not here to talk about Warren Hoyt,” she said.

“Yet he’s the reason you’re here.”

“No. I’m here because I see parallels between these two killers. I’m not the only one who does. Detective Korsak sees it, too. So let’s stick to the subject, okay?”

He regarded her with a bland smile. “Okay.”

“So what about this unsub?” She tapped on the photos. “What can you tell me about him?”

Once again, Zucker focused on the image of Dr. Yeager. “Your unknown subject is obviously organized. But you already know that. He came to the scene fully prepared. The glass cutter, the stun gun, the duct tape. He managed to subdue this couple so quickly, it makes you wonder…” He glanced at her. “No chance there’s a second perp? A partner?”

“Only one set of footprints.”

“Then your boy is very efficient. And meticulous.”

“But he left his semen on the rug. He’s handed us the key to his identity. That’s one hell of a mistake.”

“Yes, it is. And he certainly knows it.”

“So why assault her right there, in the house? Why not do it later, in a safe place? If he’s organized enough to pull off a home invasion and control the husband-”

“Maybe that’s the real payoff.”

“What?”

“Think about it. Dr. Yeager sits there, bound and helpless. Forced to watch while another man takes possession of his property.”

“Property,” she repeated.

“In this unsub’s mind, that’s what the woman is. Another man’s property. Most sexual predators wouldn’t risk attacking a couple. They’d choose the lone woman, the easy target. Having a man in the picture makes it dangerous. Yet this unsub had to know there was a husband in the picture. And he came prepared to deal with him. Could it be that was part of the pleasure, part of the excitement? That he had an audience?”

An audience of one. She looked down at the photo of Richard Yeager, slumped against the wall. Yes, that had been her immediate impression when she’d walked into the family room.

Zucker’s gaze shifted to the window. A moment passed. When he spoke again, his voice was soft and sleepy, as though the words were drifting up in a dream state.

“It’s all about power. And control. About dominance over another human being. Not just the woman, but over the man as well. Maybe it’s really the man who excites him, who’s a vital part of this fantasy. Our unsub knows the risks, yet he’s compelled to carry out his impulses. His fantasies control him, and he, in turn, controls his victims. He’s all-powerful. The dominator. His enemy sits immobilized and helpless, and our unsub does what victorious armies have always done. He’s captured his prize. He rapes the woman. His pleasure is heightened by Dr. Yeager’s utter defeat. This attack is more than sexual aggression; it’s a display of masculine power. One man’s victory over another. The conqueror claiming his spoils.”

Outside, the students on the lawn were gathering up their backpacks, brushing grass from their clothes. The afternoon sun washed everything in hazy gold. And what would the day hold next for those students? Rizzoli wondered. Perhaps an evening of leisure and conversation, pizza and beer. And a sound sleep, without nightmares. The sleep of the innocent.

Something I’ll never again know.

Her cell phone chirped. “Excuse me,” she said, and flipped open the phone.

The call was from Erin Volchko, in the hair, fiber, and trace evidence lab. “I’ve examined those strips of duct tape taken off Dr. Yeager’s body,” said Erin. “I’ve already faxed the report to Detective Korsak. But I knew you’d want to know as well.”

“What have we got?”

“A number of short brown hairs caught in the adhesive. Limb hairs, pulled from the victim when the tape was peeled off.”

“Fibers?”

“Those as well. But here’s the really interesting thing. On the strip pulled from the victim’s ankles, there was a single dark-brown hair strand, twenty-one centimeters long.”

“His wife is a blonde.”

“I know. That’s what makes this particular strand interesting.”

The unsub, thought Rizzoli. It’s from our killer. She asked, “Are there epithelial cells?”

“Yes.”

“So we might be able to get DNA off that hair strand. If it matches the semen-”

“It won’t match the semen.”

“How do you know that?”

“Because there’s no way this strand came from the killer.” Erin paused. “Unless he’s a zombie.”

For detectives in Boston P.D.‘s homicide unit, a visit to the crime lab required only a short walk down a pleasantly sun-washed hallway to the south wing of Schroeder Plaza. Rizzoli had strode down this hall countless times, her gaze often straying to the windows that overlooked the troubled neighborhood of Roxbury, where shops were barricaded at night behind bars and padlocks and every parked car came equipped with the Club. But today, she was in single-minded pursuit of answers, and she did not even glance sideways but headed in a beeline to Room S269, the hair, fiber, and trace evidence lab.

In this windowless room, crammed tight with microscopes and a gammatech prism gas chromatograph, criminalist Erin Volchko reigned supreme. Cut off from sunlight and outdoor views, she focused her gaze, instead, on the world beneath her microscope lens, and she had the pinched eyes, the perpetual squint, of someone who has been staring too long into an eyepiece. As Rizzoli came into the room, Erin swiveled around to face her.

“I’ve just put it under the microscope for you. Take a look.”

Rizzoli sat down and peered into the teaching eyepiece. She saw a hair shaft stretched horizontally across the field.

“This is that long brown strand I recovered from the strip of duct tape binding Dr. Yeager’s ankles,” said Erin. “It’s the only such strand trapped in the adhesive. The others were short hairs from the victim’s limbs, plus one of the vic’s head hairs, on the strip taken from his mouth. But this long one is an orphan strand. And it’s quite a puzzling one. It doesn’t match either the victim’s head hair or the hairs we got from the wife’s hairbrush.”

Rizzoli moved the field, scanning the hair shaft. “It’s definitely human?”

“Yes, it’s human.”

“So why can’t it be our perp’s?”

“Look at it. Tell me what you see.”

Rizzoli paused, calling back to mind all that she had learned about forensic hair examination. She knew Erin must have a reason for taking her so systematically through the process; she could hear quiet excitement in her voice. “This strand is curved, degree of curl about point one or point two. And you said the shaft length was twenty-one centimeters.”

“In the range of a woman’s hairstyle,” said Erin. “But rather long for a man.”

“Is it the length that concerns you?”

“No. Length doesn’t tell us gender.”

“Then what am I supposed to focus on, anyway?”

“The proximal end. The root. Do you notice anything strange?”

“The root end looks a little ragged. Kind of like a brush.”

“That’s exactly the word I would use. We call that a brushlike root end. It’s a collection of cortical fibrils. By examining the root, we can tell what stage of hair growth this strand was in. Care to venture a guess?”

Rizzoli focused on the bulbous root end, with its gossamerlike sheath. “There’s something transparent clinging to the root.”

“An epithelial cell,” said Erin.

“That means it was in active growth.”

“Yes. The root itself is slightly enlarged, so this hair was in late anagen. It was just ending its active growth phase. And that epithelial cell might give us DNA.”

Rizzoli raised her head and looked at Erin. “I don’t see what this has to do with zombies.”

Erin gave a soft laugh. “I didn’t mean that literally.”

“What did you mean?”

“Look at the hair shaft again. Follow it as it leads away from the root.”