"But Katy wouldn't have been there for most of that time anyway," Sam said. "She was about to go to ballet school, in London. By now she would have been gone. Didn't you know that?"

Damien almost howled, "No! I said that, I asked-you don't understand… She didn't care about being a dancer. She just liked everyone making a fuss of her. In that school, where she wouldn't have been anything special-she'd have dropped out by Christmas and come back home!"

Of all the things they had done to her, between them, this was the one that shocked me most profoundly. It was the diabolical expertise of it, the icy precision with which it targeted, annexed and defiled the one thing that had lain at Katy Devlin's heart. I thought of Simone's deep quiet voice in the echoing dance studio: Sérieuse. In all my career I had never felt the presence of evil as I felt it then: strong and rancid-sweet in the air, curling invisible tendrils up the table legs, nosing with obscene delicacy at sleeves and throats. The hairs rose on the back of my neck.

"So it was self-defense," Cassie said, after a silence in which Damien fidgeted anxiously and she and Sam didn't look at him.

Damien leaped on this. "Yes. Exactly. I mean, we wouldn't even have thought of it if there'd have been any other way."

"I understand. And you know, Damien, it's happened before: wives snapping and killing abusive husbands, stuff like that. Juries understand, too."

"Yeah?" He looked up at her with huge, hopeful eyes.

"Course. Once they hear what Rosalind went through…I wouldn't worry too much about her. OK?"

"I just don't want her to get in any trouble."

"Then you're doing the right thing by telling us all the details. OK?"

Damien sighed, a small, tired sigh with something like relief in it. "OK."

"Well done," Cassie said. "So let's keep going. When did you decide on this?"

"Like July. The middle of July."

"And when did you set the date?"

"Only, like, a few days before it happened. I had said to Rosalind, she should make sure she had a, an alibi, you know? Because we knew you guys would look at the family, she had read somewhere that the family were always the main suspects. So this one night-I think it was Friday-we met up and she said to me, she'd arranged it so she and Jessica were sleeping over at their cousins' house the next Monday and they'd be up till like two o'clock talking, so that would be the perfect night. All I had to do was make sure it was done before two o'clock; the, the police would be able to tell-"

His voice was shaking. "And what did you say?" Cassie asked.

"I…I guess I sort of panicked. I mean, it hadn't seemed real up until then, you know? I guess I hadn't thought we were actually going to do it. It was just something we talked about. It was sort of like, you know Sean Callaghan, Sean from the dig? He used to be in this band only they broke up, and he's always talking about 'Oh, when we get the band back together, when we make it big…' And, I mean, he knows they're never gonna do it, but talking about it makes him feel better."

"We've all been in that band," Cassie said, smiling.

Damien nodded. "It was like that. But then Rosalind said, 'Next Monday,' and suddenly I felt like…it just seemed like a totally crazy thing to do, you know? I said to Rosalind, maybe we should go to the police or something instead. But she freaked out. She kept saying, 'I trusted you, I really trusted you…'"

"Trusted you," Cassie said. "But not enough to make love with you?"

"No," Damien said softly, after a moment. "No, see, she had. After we first decided about Katy…it changed everything for Rosalind, knowing I'd do that for her. We…she'd given up hoping she'd ever be able to, but…she wanted to try. I was working on the dig by then, so I could afford a good hotel-she deserved something nice, you know? The first time, she…she couldn't. But we went back there the next week, and-" He bit his lips. He was trying not to cry, again.

"And after that," Cassie said, "you could hardly change your mind."

"See, that was the thing. That night, when I said maybe we should go to the police, Rosalind-she thought I'd only ever said I'd do it so I could…could get her into bed. She's so fragile, she's been hurt so badly-I couldn't let her think I was just using her. Can you imagine what it would have done to her?"

Another silence. Damien wiped a hand hard across his eyes and got himself back under control.

"So you decided to go through with it," Cassie said, evenly. He nodded, a painful, adolescent duck of the head. "How did you get Katy to come to the site?"

"Rosalind told her she had this friend on the dig who'd found a, a thing…" He mimed vaguely. "A locket. An old locket with a little painting of a dancer inside it. Rosalind told Katy it was really old and like magic or something, so she'd saved up all her money and bought it from the friend-me-as a present to bring Katy luck in ballet school. Only Katy would have to go get it herself, because this friend thought she was such a great dancer he wanted her autograph for when she was famous, and she'd have to go at night, because he wasn't allowed to sell finds, so it had to be a secret."

I thought of Cassie, as a child, hovering at the door of a groundskeeper's shed: Do you want marvels? Children think differently, she had said. Katy had walked into danger the same way Cassie had: on the unmissable off-chance of magic.

"I mean, see what I mean?" Damien said, with a note of pleading in his voice. "She totally believed that people were, like, queuing up for her autograph."

"Actually," Sam said, "she'd every reason to believe that. Plenty of people had asked for her autograph after the fund-raiser." Damien blinked at him.

"So what happened when she reached the finds shed?" Cassie asked.

He shrugged uncomfortably. "Just what I already told you. I told her the locket was in this box on a shelf behind her, and when she turned around to get it, I…I just picked up the rock and…It was self-defense, like you said, or I mean defending Rosalind, I don't know what that's called-"

"What about the trowel?" Sam asked heavily. "Was that self-defense, too?"

He stared like a bunny in headlights. "The…yeah. That. I mean, I couldn't…you know." He swallowed hard. "I couldn't do it to her. She was, she looked…I still dream about it. I couldn't do it. And then I saw the trowel on the desk, so I thought…"

"You were supposed to rape her? It's OK," Cassie said gently, at the flash of queasy panic on Damien's face, "we understand how this happened. You're not getting Rosalind into any trouble."

Damien looked uncertain, but she held his eyes steadily. "I guess," he said, after a moment. He had turned that nasty greenish-white again. "Rosalind said-she was just upset, but she said it wasn't fair that Katy would never know what Jessica had been through, so in the end I said I'd…Sorry, I think I'm gonna…" He made a sound between a cough and a gag.

"Breathe," Cassie said. "You're fine. You just need some water." She took away the shredded cup, found him a new one and filled it; she squeezed his shoulder while he sipped it, holding it in both hands, and took deep breaths.

"There you go," she said, when a little of the color had come back to his face. "You're doing great. So you were supposed to rape Katy, but instead you just used the trowel after she was dead?"

"I chickened out," Damien said into the water cup, low and savage. "She'd done way worse stuff, but I chickened out."

"Is that why"-Sam flicked the phone records with one finger-"the calls between you and Rosalind dry up after Katy died? Two calls on the Tuesday, the day after the killing; one early Wednesday morning, one the next Tuesday, then nothing. Was Rosalind annoyed with you for letting her down?"