Cassie's mobile rang. "Oh, for God's sake," she said, looking at the screen. "Hello, sir… Hello?…Sir?…Bloody phones." She hung up.

"Reception?" I said coldly.

"The fucking reception is fine," she said. "He just wanted to know when we'd be back and what was taking us so long, and I didn't feel like talking to him."

I can usually hold a sulk for much longer than Cassie, but I couldn't help it, I laughed. After a moment Cassie did, too.

"Listen," she said, "I wasn't being bitchy about Rosalind. More like worried."

"Are you thinking sexual abuse?" I realized that, somewhere in the back of my mind, I had been wondering about the same thing, but I disliked the thought so much that I had been avoiding it. One sister oversexual, one badly underweight, and one, after various unexplained illnesses, murdered. I thought of Rosalind's head bent over Jessica's and felt a sudden, unaccustomed surge of protectiveness. "The father's abusing them. Katy's coping strategy is making herself sick, either out of self-hatred or to lessen the chances of abuse. When she gets into ballet school, she decides she needs to be healthy and the cycle has to stop; maybe she confronts the father, threatens to tell. So he kills her."

"It plays," said Cassie. She was watching the trees flash past on the roadside; I could only see the back of her head. "But so does, for example, the mother-if it turns out Cooper was wrong about the rape, obviously. Munchausen by proxy. She seemed way at home in the victim role, did you notice?"

I had. In some ways grief anonymizes as powerfully as a Greek tragedy mask, but in others it pares people to the essentials (and this is, of course, the real and icy reason why we try to tell families about their losses ourselves, rather than leaving it to the uniforms: not to show how much we care, but to see how they react), and we had borne bad news often enough to know the usual variations. Most people are shocked senseless, struggling for their footing, with no idea how to do this; tragedy is new territory that comes with no guide, and they have to work out, step by dazed step, how to negotiate it. Margaret Devlin had been unsurprised, almost resigned, as though grief was her familiar default state.

"So basically the same pattern," I said. "She's making one or all of the girls sick, when Katy gets into ballet school she tries to put her foot down, and the mother kills her."

"It could explain why Rosalind dresses like a forty-year-old, too," Cassie said. "Trying to be a grown-up to get away from her mother."

My mobile rang. "Ah, fuck, man," we both said, in unison.

I did the bad-reception routine, and we spent the rest of the drive making a list of possible lines of inquiry. O'Kelly likes lists; a good one might distract him from the fact that we hadn't rung him back.

We work out of the grounds of Dublin Castle, and in spite of all the colonial connotations this is one of my favorite perks of the job. Inside, the rooms have been lovingly refurbished to be exactly like every corporate office in the country-cubicles, fluorescent lighting, staticky carpet and institution-colored walls-but the outsides of the buildings are protected and still intact: old, ornate red brick and marble, with battlements and turrets and worn carvings of saints in unexpected places. In winter, on foggy evenings, crossing the cobblestones is like walking through Dickens-hazy gold streetlamps throwing odd-angled shadows, bells pealing in the cathedrals nearby, every footstep ricocheting into darkness; Cassie says you can pretend you're Inspector Abberline working on the Ripper murders. Once, on a ringingly clear full-moon night in December, she turned cartwheels straight across the main courtyard.

There was a light in O'Kelly's window, but the rest of the building was dark: it was past seven, everyone else had gone home. We sneaked in as quietly as we could. Cassie tiptoed up to the squad room to run Mark and the Devlins through the computer, and I went down to the basement, where we keep the old case files. It used to be a wine cellar, and the crack Corporate Design Squad hasn't got around to it yet, so it's still all flagstones and columns and low-arched bays. Cassie and I have a pact to take a couple of candles down there someday, in spite of the electric lighting and in defiance of safety regulations, and spend an evening looking for secret passageways.

The cardboard box (Rowan G., Savage P., 33791/84) was exactly as I had left it more than two years before; I doubt anyone had touched it since. I pulled out the file and flipped to the statement Missing Persons had taken from Jamie's mother and, thank God, there it was: blond hair, hazel eyes, red T-shirt, cut-off denim shorts, white runners, red hair clips decorated with strawberries.

I shoved the file under my jacket, in case I ran into O'Kelly (there was no reason why I shouldn't have it, especially now that the link to the Devlin case was definite, but for some reason I felt guilty, furtive, as if I were absconding with some taboo artifact), and went back up to the squad room. Cassie was at her computer; she had left the lights off so O'Kelly wouldn't spot them.

"Mark's clean," she said. "So's Margaret Devlin. Jonathan has one conviction, just this February."

"Kiddie porn?"

"Jesus, Ryan. You have a melodramatic mind. No, disturbing the peace: he was protesting about the motorway and crossed a police line. Judge gave him a hundred-quid fine and twenty hours of community service, then upped it to forty when Devlin said that as far as he was concerned he had just been arrested for performing a community service."

That wasn't where I'd seen Devlin's name, then: as I've said, I had had only the vaguest idea that the motorway controversy even existed. But it did explain why he hadn't reported the threatening phone calls. We would not have seemed like allies to him, especially not on anything related to the motorway. "The hair clip's in the file," I said.

"Nice one," said Cassie, with a shade of a question in her voice. She was shutting down the computer and turned to look at me. "Are you pleased?"

"I'm not sure," I said. It was, obviously, nice to know that I wasn't losing my mind and imagining things; but now I was wondering whether I had actually remembered it at all or only seen it in the file, and which of those possibilities I liked less, and wishing I had just kept my mouth shut about the damn thing.

Cassie waited; in the evening light through the window her eyes looked huge, opaque and watchful. I knew she was giving me a chance to say, Fuck the hair clip, let's forget we ever found it. Even now the temptation, tired and profitless though it may be, is to wonder what would have happened if I had.

But it was late, I had had a long day, I wanted to go home, and being handled with kid gloves-even by Cassie-has always made me itch; cutting short this whole line of inquiry seemed like so much more effort than simply leaving it to run its course. "Will you ring Sophie about the blood?" I asked. In that dim room, it seemed all right to admit this much weakness at least.

"Sure," said Cassie. "Later, though, OK? Let's go talk to O'Kelly before he has an aneurysm. He texted me while you were in the basement; I didn't think he even knew how to do that, did you?"

I rang O'Kelly's extension and told him we were back, to which he said, "About fucking time. What did you do, stop for a quickie?" and then told us to get into his office pronto.

The office has only one chair apart from O'Kelly's own, one of those faux-leather ergonomic things. The implication is that you shouldn't take up too much of his space or time. I sat in the chair, and Cassie perched on a table behind me. O'Kelly gave her an irritated look.