“Most likely something small and razor-sharp, perhaps even designed especially for the job. Here’s the other point of consideration. Often in these kinds of crimes, the killer will eventually set down his weapon. You know, resting for a moment, readjusting his grip, or even laying down the knife while getting on and off the bed. A reflexive movement, not even thought about, but an act that leaves a bloody imprint of the blade behind as further evidence. In a case where a killer spends this much time with a body at a scene this bloody, it’s the kind of evidence you’d almost expect. Except . . .”

“He didn’t do it.”

“Or he was aware enough, controlled enough, to rest it in the middle of another bloodstain, the kind of place where he thought it wouldn’t leave a pattern.”

D.D. glanced at her husband. “You just said he thought it wouldn’t leave a pattern . . . ?”

Alex smiled faintly. He had returned to the bloody sheet hanging on the wall and was hitting it up close and personal with the beam from his flashlight. “In this kind of attack, where the victim is bleeding out from multiple wounds over an extended period of time—”

“That’s one way of putting it.”

“You get blood-on-blood patterns. Blood, as it starts to dry, thickens, the edges turning yellow from hemoglobin that’s separating from the platelets. The old blood starts to form a surface for the new blood to drip upon.”

She could almost picture this. “Meaning if the killer set down a knife covered in fresh blood upon an area of drying blood, it could leave an imprint on the surface of the old blood.”

“Precisely.”

“And in this case . . .”

Alex, his face a mere two inches from the stiff, red-encrusted surface: “I think . . . I can see an outline. Faint, but there. I would guess a filleting knife, but to be fair, it’s hard to know sometimes if you’re seeing what you want to see or what’s really there. We can fine-tune this, however, enhance the contrast using some chemicals back at the lab. Certainly it’s worth pursuing.”

“Certainly,” she agreed.

He frowned one more time, peering intently. For the sake of argument, D.D. did the same, but the nuance of a stain within a stain was lost on her. Mostly, she was aware of the overwhelming stench of blood. So much. This sheet. This mattress.

And yet, as she turned around, not in the rest of the room.

Alex followed her lead, once more sweeping the walls and floors with the high-intensity beam, as they considered the final step of the murderer’s process.

“Cleanup,” D.D. muttered.

“Definitely,” Alex concurred. “He cleaned up.”