“I’m guessing special forces. Stabbing’s messy business, but this guy has it down to a science.”

“All right,” D.D. said briskly. “Mom’s down. Oldest son is down. Now what?”

“Got two left. Twelve-year-old girl, nine-year-old boy. Probably hoped to take them one at a time, but turns out both of them are in her room.”

Alex vacated the blue room and they proceeded single file down the hallway again. This time the blood spatter turned, leading them through a doorway into a bright pink room bearing purple window valances and half a dozen posters of Hannah Montana and the Jonas Brothers.

“Now things are a little more complicated here, as you can see.” Alex gestured to the floor, which was a dizzying array of spray droplets, blood pools, and yellow evidence placards. “I’m guessing, purely to judge by the condition of the bodies, that he got the boy first.”

“Why the boy?”

“Single mortal wound. Look at the bed.”

D.D. belatedly realized the purple comforter wasn’t really purple. It used to be a dark pink, the original color now skewed by another sizable pool of blood, with a matching spray pattern arcing across the opposite wall.

“The kids knew,” Alex said, more softly now, less academic. “No closets in the room. So they huddled in the corner. Brother and sister together, taking a last stand. The subject came in. He must’ve been a sight by then. Covered in back spray from hammering down the first death blow, let alone the second. Kids stood shoulder to shoulder, next to the bed.

“Boy broke first, that’s my guess,” Alex continued. “Tried to get around the subject by springing up onto the bed. Didn’t work. Subject sliced open the kid’s throat as the boy attempted to bolt past. Game over. Girl’s probably screaming by then. But she doesn’t freeze, which is interesting. Most people facing such a scene …”

Alex’s voice faded, then he cleared his throat, continued on: “The girl runs. Takes advantage of her own brother’s death to sprint for the front door. Of all of them, she’s the only one who gets a chance. He wounds her. Right here.” Alex pointed with his pencil to a round smeared spot. “Maybe the subject was aiming for her neck, but got her shoulder instead. The blow knocked her off balance, hence smudge here and smudge there, probably made by her feet, but she keeps on trucking, God bless her.

“Gets halfway down that hallway, running the race of her life. And then—”

“He catches her,” D.D. fills in, then pauses. “But doesn’t kill her? Drags her away?”

Alex shrugged. “Who knows? She’s the last one left and he has her incapacitated. Maybe he realized he didn’t have to rush. Or maybe he just wanted her to suffer a little more. She got away. That pissed him off.”

“Sexual assault?” D.D. asked.