“But . . . but . . . ,” D.D. found herself sputtering. Then, more firmly: “Not possible. No way you can fillet a human being without being positively coated in blood yourself. And no way the killer could then move around this room, let alone exit the house, without leaving an obvious trail. Even if he cleaned up after himself with a bleach-soaked mop, you can’t get it all. It’s the whole magic of your job. Even when you can no longer see blood with the human eye, it lingers, just waiting for the right high-intensity beams or proper chemical solution to tell its tale. This”—she waved her hand toward the relatively blood-free expanse of hardwood floor—“I’m seeing it, but I’m not believing it.”

“As I mentioned, the Boston PD wouldn’t mind some help with this one.” Alex walked deeper into the room, his beam sweeping methodically right, left, right. “Shall we start with the bedsheet? I believe it serves as the beginning of the story.”

She nodded once. Responding to his hand signal, she obediently killed the overhead lights. In the near gloom, it was easier to focus on Alex’s high-intensity light and the way it cast a single fitted sheet into a terrible inkblot of dark, deadly stains.

Blood patterns, D.D. had learned by now, varied depending on the velocity of the blow and the porosity of the surface area. Bedding, such as blankets and mattresses, was obviously very soft and porous, meaning the blood spatter soaked straight in versus ricocheting or forming a starburst pattern on impact. In fact, the white sheet now bore a single, very long, almost cylinder-shaped bloody print, broken in two places by bars of white. She and Alex both stepped closer, inspecting the outer edges of the print.

“I don’t see any signs of fine mist,” D.D. murmured, “such as blowback from high-velocity gunfire.”

“Victim wasn’t shot. Blood patterns indicate a low-velocity impact.”

Which was consistent with most stabbings, D.D. knew. She still frowned. “But there’s no spatter at all, not even random drippings from the handle of the knife or edge of the blade. How do you explain that?”

“Killer’s not stabbing. Cause of death is unknown. But given the lack of defensive wounds, arterial spray and spatter, the victim was dead before the killer began removing her skin. I’m just a criminalist, not a behavioralist, but it would appear the crime is about control, not about pain and suffering. What we’re seeing here is purely the result of postmortem work.”

It should’ve been a reassuring thought. That the victim was already dead before the first slip of the cold blade beneath the surface of her skin . . . And yet, D.D. found herself almost slightly more horrified. A sexual-sadist predator with an overwhelming compulsion to inflict pain and suffering was something she could almost understand. But this . . . a killer who skinned his victims for sport?