"How's that?" I took the cigarette packet back and tilted it at Sam, who looked like he could do with one, but he shook his head.

"I mean, he could've dumped her in the wood or somewhere, where she might not have been found for ages, or even just on the ground. Instead, he went out of his way to put her on that altar. It could be a display thing, but I don't think so: he didn't pose her, except to leave her lying on her left side, so the head injury was hidden-again, trying to minimize the crime. I think he was trying to treat her with care, respect-keep her away from animals, make sure she was found soon." She reached for the ashtray. "The good thing is, if it's a schizophrenic falling apart, he should be fairly easy to spot."

"What about a hired killer?" I asked. "That would explain the reluctance, too. Someone-maybe the mystery phone caller-hired him to do it, but he didn't have to like the job."

"Actually," Cassie said, "a hired killer-not a professional; an amateur who needed the money badly-might fit even better. Katy Devlin sounded like a fairly sensible kid, wouldn't you say, Rob?"

"She sounds like the most well-adjusted person in that whole family."

"Yeah, to me, too. Smart, focused, strong-willed-"

"Not the type to go off at night with a stranger."

"Exactly. Especially not a stranger who's clearly not all there. A schizophrenic going to pieces probably wouldn't be able to act normal enough to get her to go anywhere with him. More likely this person is presentable, pleasant, good with kids-someone she'd known for a while. Someone she felt comfortable with. He didn't seem like a threat."

"Or she," I said. "How much did Katy weigh?"

Cassie flipped through the notes. "Seventy-eight pounds. Depending on how far she was carried, yeah, a woman could have done it, but it would have to be a pretty strong woman. Sophie didn't find any drag marks at the dump site. Just statistically speaking, I'd bet on a guy."

"But we're eliminating the parents?" Sam said hopefully.

She made a face. "No. Say one of them was abusing her and she was threatening to tell: either the abuser or the other parent could have felt she had to die, in order to protect the whole family. Maybe they tried to stage a sex crime but didn't have the heart to do it thoroughly… Basically, the only thing I'm more or less sure of is that we're not looking for a psychopath or a sadist-our guy couldn't dehumanize her and didn't enjoy seeing her suffer. We're looking for someone who didn't want to do it, someone who felt he was doing it out of necessity. I don't think he'll insert himself into the investigation-he won't be getting off on all the attention, nothing like that-and I don't think he'll do it again any time soon, not unless he feels threatened somehow. And he's almost definitely local. A real profiler could probably be a lot more specific, but…"

"You got your degree at Trinity, right?" Sam said.

Cassie gave a quick shake of her head, reached for more cherries. "I dropped out in fourth year."

"Why'd you do that?"

She spat a cherry stone into her palm and gave Sam a smile I knew, an exceptionally sweet smile that scrunched up her face till you couldn't see her eyes. "Because what would you people do without me?"

I could have told him she wouldn't answer. I had asked her that question several times, over the years, and got answers ranging from "There was nobody of your caliber to annoy" to "The food in the Buttery sucked." There has always been something enigmatic about Cassie. This is one of the things I like in her, and I like it all the more for being, paradoxically, a quality that isn't readily apparent, elusiveness brought to so high a level it becomes almost invisible. She gives the impression of being startlingly, almost childishly open-which is true, as far as it goes: what you see is in fact what you get. But what you don't get, what you barely glimpse: this is the side of Cassie that fascinated me always. Even after all this time I knew there were rooms inside her that she had never let me guess at, let alone enter. There were questions she wouldn't answer, topics she would discuss only in the abstract; try to pin her down and she would skim away laughing, as nimbly as a figure skater.

"You're good," Sam said. "Degree or no degree."

Cassie raised one eyebrow. "Wait and see if I'm right before you say that."

"Why did he keep her for a day?" I asked. This had been bothering me all along-because of the obvious hideous possibilities, and because of the nagging suspicion that, if he hadn't needed to get rid of her for some reason, he might have kept her for longer, kept her forever; she might have vanished as silently and finally as Peter and Jamie had.

"If I'm right about all the other stuff, the distancing himself from the crime, then it wasn't because he wanted to. He would've wanted to get rid of her as soon as possible. He kept her because he didn't have a choice."

"He lives with someone and had to wait till they were out of the way?"

"Yeah, could be. But I was wondering if maybe the dig wasn't a random choice. Maybe he had to dump her there-either because it's part of whatever grand plan he's following, or because he doesn't have a car and the dig was the only place handy. That would fit in with what Mark said about not seeing a car go past-and it would mean the kill site's somewhere very nearby, probably in one of the houses at that end of the estate. Maybe he tried to dump her on Monday night, but Mark was there in the woods, with his fire. The killer could have seen him and been scared off; he had to hide Katy and try again the next night."

"Or the killer could have been him," I said.

"Alibi for Tuesday night."

"From a girl who's mad about him."

"Mel's not the ditzy stand-by-your-man type. She's got a mind of her own, and she's plenty smart enough to realize how important this is. If Mark had jumped out of bed halfway through the action to take a nice long walk, she'd have told us."

"He could have an accomplice. Either Mel or someone else."

"And what, they hid the body on the grassy knoll?"

"What's your boy's motive?" Sam inquired. He had been eating cherries and watching us with interest.

"His motive is he's several hundred yards out of his tree," I told him. "You didn't hear him. He's perfectly normal on most things-normal enough to reassure a kid, Cass-but get him talking about the site and he starts going on about sacrilege and worship… The site's under threat from this motor-way: maybe he thought a nice human sacrifice to the gods, just like old times, would get them to step in and save it. When it comes to this site, he's batty."

"If this turns out to be a pagan sacrifice," Sam said, "dibs I not be the one to tell O'Kelly."

"I vote we get him to tell O'Kelly himself. And we sell tickets."

"Mark is not batty," Cassie said firmly.

"Oh, he is, too."

"He is not. His work is the center of his life. That's not batty."

"You should have seen them," I told Sam. "Honestly, it was more like a date than an interrogation. Maddox nodding away, fluttering her eyelashes, telling him she knew exactly how he feels-"

"Which I do, actually," Cassie said. She abandoned Cooper's notes and pulled herself backward onto the futon. "And I did not either flutter my eyelashes. When I do, you won't miss it."

"You know how he feels? What, you pray to the Heritage God?"

"No, you big eejit. Shut up and listen. I have a theory about Mark." She kicked off her shoes, tucked her feet up under her.

"Oh, God," I said. "Sam, I hope you're not in a hurry."

"I always have time for a good theory," Sam said. "Can I have a drink to go with it, if we've finished working?"

"Wise move," I told him.

Cassie shoved me with her foot. "Find whiskey or something." I slapped her foot away and got up. "OK," she said, "we all need to believe in something, right?"