"If you were under arrest," Cassie said, dumping the file on the table, "you'd know all about it. What did you think you might be under arrest for?"

Jonathan shrugged. She smiled at him and pulled out a chair, facing the scary wall. "Have a seat." After a moment, he slowly took off his coat and sat down.

I took him through the update. I was the one he had trusted with his story, and that trust was a small close-range weapon that I didn't intend to detonate until the right moment. For now, I was his ally. I was, to a large extent, honest with him. I told him about the leads we had followed up, the tests the lab had run. I listed for him, one by one, the suspects we had identified and eliminated: the locals who thought he was stopping progress, the pedophiles and confession junkies and Tracksuit Shadows, the guy who thought Katy's leotard was immodest; Sandra. I could feel the frail, mute army of photographs ranged behind me, waiting. Jonathan did well, he kept his eyes on mine almost all the time; but I could see the effort of will that went into it.

"So what you're telling me is that you're getting nowhere," he said eventually, heavily. He looked terribly tired.

"God, no," Cassie said. She had been sitting at the corner of the table, chin propped on one palm, watching in silence. "Not at all. What Detective Ryan is telling you is that we've come a long way, these last few weeks. We've done a lot of eliminating. And here's what we've got left." She inclined her head towards the wall; he didn't take his eyes off her face. "We've got evidence that your daughter's murderer is a local man with intimate knowledge of the Knocknaree area. We've got forensic evidence linking her death to the 1984 disappearances of Peter Savage and Germaine Rowan, which indicates that the murderer is probably aged at least thirty-five and has had strong ties to the area for over twenty years. And a lot of the men fitting that description have alibis, so that narrows it down even further."

"We also have evidence," I said, "to suggest that this isn't some thrill killer. This man isn't killing at random. He's doing it because he feels he has no choice."

"So you think he's insane," Jonathan said. His mouth twisted. "Some lunatic-"

"Not necessarily," I said. "I'm just saying that sometimes situations get out of hand. Sometimes they end in tragedies that nobody really wanted to happen."

"So you see, Mr. Devlin, that narrows it down again: we're looking for someone who knew all three children and had motive to want them dead," Cassie said. She was tilting her chair back, hands behind her head, her eyes steady on his. "We're going to get this guy. We're getting closer every day. So if there's anything you want to tell us-anything at all, about either case-this is the time to do it."

Jonathan didn't answer immediately. The room was very quiet, only the soft drone of the fluorescent bars overhead and the slow, monotonous creak of Cassie rocking her chair on its back legs. Jonathan's eyes fell away from hers and moved past her, across the photographs: Katy suspended in that impossible arabesque, Katy laughing on a blurry green lawn with her hair blown sideways and a sandwich in her hands, Katy with one eye a slit open and blood crusted dark on her lip. The bare, simple pain on his face was almost indecent. I had to force myself not to look away.

The silence stretched tighter. Almost imperceptibly, something I recognized was happening to Jonathan. There's a specific crumbling in the mouth and spine, a sagging as though the underlying musculature is dissolving to water, that every detective knows: it belongs to the instant before a suspect confesses, as he finally and almost with relief lets his defenses fall away. Cassie had stopped rocking her chair. My pulse was running high in my throat, and I felt the photographs behind me catch tiny swift breaths and hold them, poised to swoop off the paper and down the corridor and out into the dark evening, freed, if only he gave the word.

Jonathan wiped a hand hard across his mouth and folded his arms and looked back at Cassie. "No," he said. "There's nothing."

Cassie and I let out our breath in unison. I had known, really, that it was too much to hope for, so soon, and-after that first sinking second-I hardly cared; because now, at last, I was sure that Jonathan knew something. He had as good as told us so.

This actually came as something of a shock. The whole case had been so crowded with possibilities and hypotheticals ("OK. So say just for a second that Mark did do it, right, and the illness and the old case aren't related after all, and say Mel's telling the truth: who could he have got to dump the body?") that certainty had started to seem unimaginable, some remote childhood dream. I felt as if I had been moving among empty dresses hung in some dim attic and had suddenly bumped smack into a human body, warm and solid and alive.

Cassie eased the front legs of her chair to the floor. "OK," she said, "OK. Let's go back to the beginning. The rape of Sandra Scully. When did that happen, exactly?"

Jonathan's head turned sharply towards me. "You're all right," I told him, in an undertone. "Statute of limitations." In fact, we still hadn't bothered to check this, but it was moot: there was no chance we would ever be able to charge him, anyway.

He gave me a long, wary look. "Summer of '84," he said, finally. "I wouldn't know the date."

"We've got statements putting it in the first two weeks of August," Cassie said, opening the file. "Does that sound right to you?"

"Could well have been."

"We also have statements saying that there were witnesses."

He shrugged. "I wouldn't know."

"Actually, Jonathan," Cassie said, "we've been told that you chased them into the woods and came back saying, 'Bloody kids.' Sounds to me like you knew they were there."

"Maybe I did. I don't remember."

"How did you feel about the fact that there were kids out there who knew what you'd done?"

Another shrug. "Like I said. I don't remember that."

"Cathal says…" She flipped pages. "Cathal Mills says you were terrified they'd go to the cops. He says you were, quote, so scared you were practically shitting your pants, unquote."

No response. He settled deeper into the chair, arms folded, solid as a wall.

"What'd you do to stop them turning you in?"

"Nothing."

Cassie laughed. "Ah, come on, Jonathan. We know who those witnesses were."

"You've one up on me, then." His face was still braced into hard angles, giving away nothing, but a red flush was building across his cheeks: he was getting angry.

"And only a few days after the rape," Cassie said, "two of them disappeared." She got up-unhurriedly, stretching-and crossed the room to the wall of photos.

"Peter Savage," she said, laying a finger on his school picture. "I'd like you to look at the photograph, please, Mr. Devlin." She waited until Jonathan's head came up and he stared, defiantly, at the picture. "People say he was a born leader. He might have been heading up the Move the Motorway campaign with you, if he'd lived. His parents can't move house, do you know that? Joseph Savage got offered his dream job, a few years back, but it would've involved moving to Galway, and they couldn't bear the thought that Peter might come home someday and find them gone."

Jonathan began to say something, but she didn't give him time. "Germaine Rowan"-her hand moved to the next picture-"a.k.a. Jamie. She wanted to be a vet when she grew up. Her mother hasn't moved a thing in her room. She dusts it every Saturday. When the phone numbers went to seven digits, back in the nineties-remember that?-Alicia Rowan went into Telecom Éireann's head office and begged them, in tears, to let her keep the old six-digit one, in case someday Jamie tried to ring home."