"Margaret loves our girls," Jonathan said. His voice was taut, over-tightened. "She would never-"

"Never what?" inquired Cassie. "She'd never make Katy sick, or she'd never kill her?"

"Never do anything to hurt her. Ever."

"Then who does that leave?" Cassie asked. She was leaning against the wall, fingering the post-mortem photo and watching him, cool as a girl in a painting. "Rosalind and Jessica both have a rock-solid alibi for the night Katy died. Who's left?"

"Don't you dare even suggest I hurt my daughter," he said, a low, warning rumble. "Don't you dare."

"We've got three murdered children, Mr. Devlin, all murdered in the same place, all very probably murdered to cover up other crimes. And we've got one guy smack bang in the middle of each case: you. If you've got a good explanation for that, we need to hear it now."

"This is unbefuckinglievable," Jonathan said. His voice was rising dangerously. "Katy's-someone's after killing my daughter and you want me to give you an explanation? That's your bloody job. You're the ones should be giving me explanations, not accusing me of-"

I was on my feet almost before I knew it. I threw down my notebook with a flat smack and pitched myself forward on my hands, leaning across the table into his face. "A local guy, Jonathan, thirty-five or over, been living in Knocknaree more than twenty years. A guy with no solid alibi. A guy who knew Peter and Jamie, had daily access to Katy, and had a strong motive to kill all of them. Who the fuck does that sound like to you? You name me one other man who fits that description, and I swear to God you can walk out that door and we'll never hassle you again. Come on, Jonathan. Name one. Just one."

"Then arrest me!" he roared. He slammed out his fists at me, palms up, wrists pressed together. "Come on, if you're so bloody sure, all your evidence-Arrest me! Come on!"

I cannot tell you, I wonder if you can imagine, how badly I wanted to do it. My whole life was shooting through my mind as a drowning man's is said to-tear-sodden nights in a chilly dorm and bikes zigzagging look-Ma-no-hands, pocket-warm butter-and-sugar sandwiches, the detectives' voices yammering endlessly at my ears-and I knew we didn't have enough, it would never stick, in twelve hours he would walk out that door free as a bird and guilty as sin. I had never been so sure of anything in my life. "Fuck this," I said, shoving up my shirt cuffs. "No, Devlin. No. You've been sitting here bullshitting us all evening, and I've had enough."

"Arrest me or-"

I lunged at him. He leaped backwards, sending the chair clattering, finding a corner and throwing up his fists in the same reflexive movement. Cassie was on me already, grabbing my raised arm with both hands. "Jesus, Ryan! Stop!"

We had done it so many times. It's our last resort, when we know a suspect is guilty but we need a confession and he won't talk. After the lunge and grab I slowly relax, shake off Cassie's loosening hands, still glaring at the suspect; finally roll my shoulders and stretch out my neck and sprawl in my chair, drumming my fingers restlessly, while she goes back to questioning him with a watchful eye on me for any sign of renewed ferocity. A few minutes later she starts, checks her mobile, says, "Dammit, I have to take this. Ryan…just stay cool, OK? Remember what happened last time," and leaves us alone together. It works; mostly I don't even have to stand up again. Ten times we'd done it, twelve? We had it as smoothly choreographed as any screen stunt.

But this wasn't the same, this was the real thing for which all the other times and all the other cases had been nothing but practice, and it infuriated me even more that Cassie didn't realize this. I tried to jerk my arm away; she was stronger than I expected, wrists like steel, and I heard a seam rip somewhere in my sleeve. We swayed in a thick, clumsy struggle. "Get off me-"

"Rob, no-"

Her voice came to me thin and meaningless through the huge red roaring in my head. All I could see was Jonathan, brows down and chin braced like a boxer, cornered and waiting only a few feet away. I reefed my arm forward with all my strength and felt her stumble back as her grip slipped away, but the chair got under my feet and before I could kick it aside and reach him she had recovered, caught my other arm and twisted it up behind my back, one fast, clinical move. I gasped.

"Are you out of your fucking mind?" she said straight into my ear, low and furious. "He doesn't know anything."

The words hit me like a slap of cold water in the face. I knew that even if she was wrong there was nothing in the world I could do about it, and it left me breathless, helpless. I felt as if I had been filleted.

Cassie felt the fight drain out of me. She shoved me away and stepped back swiftly, her hands still tense and ready. We stared at each other across the room like enemies, both of us breathing hard.

There was something dark and spreading on her lower lip, and after a moment I realized it was blood. For a hideous, free-falling second I thought I had hit her. (Later I found out that I hadn't, in fact: when I pulled away, the recoil flung one of her wrists back to smack her in the mouth, cutting her lip on her front teeth; not that this makes much of a difference.) It brought me back to myself, a little. "Cassie-" I said.

She ignored me. "Mr. Devlin," she said coolly, as if nothing at all had happened; there was only the faintest hint of a tremor in her voice. Jonathan-I had forgotten he was there-moved slowly out of the corner, his eyes still on me. "We'll be releasing you without charge for now. But I would strongly advise you to stay where we can find you and not to attempt to contact your rape victim in any way. Understood?"

"Yeah," Devlin said, after a moment. "Fine." He yanked the chair upright, pulled his tangled coat off the back and threw it on in quick, angry jabs. At the door he turned and gave me a hard look, and I thought for a moment he was going to say something, but he changed his mind and left, shaking his head disgustedly. Cassie followed him out and whipped the door shut behind her; it was too heavy for a proper slam, it closed with an unsatisfying thump.

I sank into a chair and put my face in my hands. I had never done anything like this before, ever. I abhor physical violence, I always have; the very thought makes me flinch. Even when I was a prefect, with arguably more power and less accountability than any adult outside of small South American countries, I never once caned anyone. But a minute ago I had been tussling with Cassie like some drunk in a bar brawl, ready to dogfight Jonathan Devlin on the interview-room floor, swept away by the overwhelming desire to knee him in the guts and beat his face to bloody pulp. And I had hurt Cassie. I wondered, with detached, lucid interest, whether I was losing my mind.

After a few minutes Cassie came back in, shut the door and leaned against it, hands shoved into her jeans pockets. Her lip had stopped bleeding.

"Cassie," I said, rubbing my hands over my face. "I'm really sorry. Are you OK?"

"What the hell was that?" She had a hot, bright spot of color on each cheekbone.

"I thought he knew something. I was sure." My hands were shaking so hard it looked phony, like an inept actor simulating shock. I clasped them together to stop it.

Eventually she said, very quietly, "Rob, you can't keep this up." I didn't answer. After a long time, I heard the door close behind her.