As Strike approached Henlys Corner on the North Circular Road the following afternoon, he saw, with a muttered oath, that traffic ahead had come to a halt. The junction, which was a notorious hotspot for congestion, had supposedly been improved earlier that year. As he joined the stationary queue, Strike wound down his window, lit a cigarette and glanced at his dashboard clock, with the familiar sensation of angry impotence that driving in London so often engendered. He had wondered whether it might be wiser to take the Tube north, but the psychiatric hospital lay a good mile from the nearest station, and the BMW was marginally easier on his still sore leg. Now he feared that he was going to be late for an interview that he was determined not to miss, firstly because he had no wish to disoblige the psychiatric team who were letting him see Billy Knight, and secondly because Strike didn’t know when there would next be an opportunity to speak to the younger brother without fear of running into the older. Barclay had assured him that morning that Jimmy’s plans for the day comprised writing a polemic on Rothschild’s global influence for the Real Socialist website and sampling some of Barclay’s new stash.

Scowling and tapping his fingers on the steering wheel, Strike fell back to ruminating on a question that had been nagging at him since the previous evening: whether or not the cut connection halfway through his call to Robin had really been due to Matthew snatching the phone out of her hand. He had not found Robin’s subsequent assurances that all was well particularly convincing.

While heating himself baked beans on his one-ringed hob, because he was still attempting to lose weight, Strike had debated calling Robin back. Eating his meatless dinner unenthusiastically in front of the television, supposedly watching highlights of the Olympics closing ceremony, his attention was barely held by the sight of the Spice Girls zooming around on top of London cabs. I think marriage is nearly always an unfathomable entity, even to the people inside it, Della Winn had said. Perhaps Robin and Matthew were even now in bed together. Was pulling a phone out of her hand any worse than deleting her call history? She had stayed with Matthew after that. Where was her red line?

And Matthew was surely too careful of his own reputation and prospects to abandon all civilized norms. One of Strike’s last thoughts before falling asleep the night before had been that Robin had successfully fought off the Shacklewell Ripper, a grisly reflection, perhaps, but one that brought a certain reassurance.

The detective was perfectly aware that the state of his junior partner’s marriage ought to be the least of his worries, given that he so far had no concrete information for the client who was currently paying three full-time investigators to find out the facts about her father’s death. Nevertheless, as the traffic finally moved on, Strike’s thoughts continued to eddy around Robin and Matthew until at last he saw a signpost to the psychiatric clinic and, with an effort, focused his mind on the forthcoming interview.

Unlike the gigantic rectangular prism of concrete and black glass where Jack had been admitted a few weeks earlier, the hospital outside which Strike parked twenty minutes later boasted crocketed spires and byzantine windows covered with iron bars. In Strike’s opinion it looked like the bastard offspring of a gingerbread palace and a gothic prison. A Victorian stonemason had carved the word “Sanatorium” into the dirty redbrick arch over the double doorway.

Already five minutes late, Strike flung open the driver’s door and, not bothering to change his trainers for smarter footwear, locked the BMW and hurried, limping, up the grubby front steps.

Inside he found a chilly hallway with high, off-white ceilings, churchlike windows and a general suspicion of decay barely kept at bay by the fug of disinfectant. Spotting the ward number he had been given by phone, he set off along a corridor to the left.

Sunlight falling through the barred windows cast striped patches onto the off-white walls, which were hung crookedly with art, some of which had been done by former patients. As Strike passed a series of collages depicting detailed farmyard scenes in felt, tinsel and yarn, a skeletal teenage girl emerged from a bathroom alongside a nurse. Neither of them seemed to notice Strike. Indeed, the girl’s dull eyes were focused, it seemed to him, inward upon a battle she was waging far from the real world.

Strike was faintly surprised to discover the double doors to the locked ward at the end of the ground floor corridor. Some vague association with belfries and Rochester’s first wife had led him to picture it on an upper floor, hidden perhaps in one of those pointed spires. The reality was entirely prosaic: a large green buzzer on the wall, which Strike pressed, and a male nurse with bright red hair peering through a small glass window, who turned to speak to somebody behind him. The door opened and Strike was admitted.

The ward had four beds and a seating area, where two patients in day clothes were sitting, playing drafts: an older, apparently toothless man and a pale youth with a thickly bandaged neck. A cluster of people were standing around a workstation just inside the door: an orderly, two more nurses, and what Strike assumed to be two doctors, one male, one female. All turned to stare at him as he entered. One of the nurses nudged the other.

“Mr. Strike,” said the male doctor, who was short, rather foxy in appearance and had a strong Mancunian accent. “How do you do? Colin Hepworth, we spoke on the phone. This is my colleague, Kamila Muhammad.”

Strike shook hands with the woman, whose navy trouser suit reminded him of a policewoman’s.

“We’re both going to be sitting in on your interview with Billy,” she said. “He’s just gone to the bathroom. He’s quite excited about seeing you again. We thought we’d use one of our interview rooms. It’s right here.”

She led him around the workstation, the nurses still watching avidly, into a small room containing four chairs and a desk that had been bolted to the floor. The walls were pale pink but otherwise bare.

“Ideal,” said Strike. It was like a hundred interview rooms he had used in the military police. There, too, third parties had often been present, usually lawyers.

“A quick word before we start,” said Kamila Muhammad, pulling the door to on Strike and her colleague, so that the nurses couldn’t hear their conversation. “I don’t know how much you know about Billy’s condition?”

“His brother told me it’s schizoid affective disorder.”

“That’s right,” she said. “He went off his medication and ended up in a full-blown psychotic episode, which by the sounds of it is when he came to see you.”

“Yeah, he seemed pretty disturbed at the time. He looked as though he’d been sleeping rough, as well.”

“He probably had been. His brother told us he’d been missing around a week at that point. We don’t believe Billy’s psychotic anymore,” she said, “but he’s still quite closed down, so it’s hard to gauge to what degree he’s engaged with reality. It can be difficult to get an accurate picture of someone’s mental state where there are paranoid and delusional symptoms.”

“We’re hoping that you can help us disentangle some of the facts from the fiction,” said the Mancunian. “You’ve been a recurring motif in his conversation ever since he was sectioned. He’s been very keen to talk to you, but not so much to any of us. He’s also expressed fear of—of repercussions if he confides in anyone and, again, it’s difficult to know whether that fear is part of his illness or, ah, whether there’s someone who he genuinely has reason to fear. Because, ah—”

He hesitated, as though trying to choose his words carefully. Strike said:

“I’d imagine his brother could be scary if he chose to be,” and the psychiatrist seemed relieved to have been understood without breaking confidentiality.

“You know his brother, do you?”

“I’ve met him. Does he visit often?”

“He’s been in a couple of times, but Billy’s often been more distressed and agitated after seeing him. If he seems to be similarly affected during your interview—” said the Mancunian.

“Understood,” said Strike.

“Funny, really, seeing you here,” said Colin, with a faint grin. “We assumed that his fixation with you was all part of his psychosis. An obsession with a celebrity is quite common with these kinds of disorders… As a matter of fact,” he said candidly, “just a couple of days ago, Kamila and I were agreeing that his fixation with you would preclude an early discharge. Lucky you called, really.”

“Yeah,” said Strike drily, “that is lucky.”

The redheaded male nurse knocked on the door and put his head in.

“That’s Billy ready to talk to Mr. Strike.”

“Great,” said the female psychiatrist. “Eddie, could we get some tea in here? Tea?” she asked Strike over her shoulder. He nodded. She opened the door. “Come in, Billy.”

And there he was: Billy Knight, wearing a gray sweatshirt and jogging pants, his feet in hospital slippers. The sunken eyes were still deeply shadowed, and at some point since he and Strike had last seen each other, he had shaven his head. The finger and thumb of his left hand were bandaged. Even through the tracksuit that somebody, presumably Jimmy, had brought him to wear, Strike could tell that he was underweight, but while his fingernails were bitten to bloody stubs and there was an angry sore at the corner of his mouth, there was no longer an animal stench about him. He shuffled inside the interview room, staring at Strike, then held out a bony hand, which Strike shook. Billy addressed the doctors.

“Are you two going to stay?”

“Yes,” said Colin, “but don’t worry. We’re going to keep quiet. You can say whatever you like to Mr. Strike.”

Kamila positioned two chairs against the wall and Strike and Billy sat down opposite each other, the desk between them. Strike could have wished for a less formal configuration of furniture, but his experience in Special Investigation Branch had taught him that a solid barrier between questioner and interviewee was often useful, and doubtless this was just as true on a locked psychiatric ward.

“I’ve been trying to find you, since you first came to see me,” Strike said. “I’ve been quite worried about you.”

“Yeah,” said Billy. “Sorry.”

“Can you remember what you said to me at the office?”

Absently, it seemed, Billy touched his nose and his sternum, but it was a ghost of the tic he had exhibited in Denmark Street, and almost as though he sought to remind himself how he had felt then.

“Yeah,” he said, with a small, humorless smile. “I told you about the kid, up by the horse. The one I saw strangled.”

“D’you still think you witnessed a child being strangled?” asked Strike.

Billy raised a forefinger to his mouth, gnawed at the nail and nodded.

“Yeah,” he said, removing the finger. “I saw it. Jimmy says I imagined it because I’m—you know. Ill. You know Jimmy, don’t you? Went to the White Horse after him, didn’t you?” Strike nodded. “He was fucking livid. White Horse,” said Billy, with a sudden laugh. “That’s funny. Shit, that’s funny. I never even thought of that before.”

“You told me you saw a child killed ‘up by the horse.’ Which horse did you mean?”

“White Horse of Uffington,” said Billy. “Big chalk figure, up on the hill, near where I grew up. Doesn’t look like a horse. More like a dragon and it’s on Dragon Hill, as well. I’ve never understood why they all say it’s a horse.”

“Can you tell me exactly what you saw up there?”

Like the skeletal girl Strike had just passed, he had the impression that Billy was staring inside himself, and that outer reality had temporarily ceased to exist for him. Finally, he said quietly:

“I was a little kid, proper little. I think they’d given me something. I felt sick and ill, like I was dreaming, slow and groggy, and they kept trying to make me repeat words and stuff and I couldn’t speak properly and they all thought it was funny. I fell over in the grass on the way up. One of them carried me for a bit. I wanted to sleep.”

“You think you’d been given drugs?”

“Yeah,” said Billy dully. “Hash, probably, Jimmy usually had some. I think Jimmy took me up the hill with them to keep my father from knowing what they’d done.”

“Who do you mean by ‘they’?”

“I don’t know,” said Billy simply. “Grown-ups. Jimmy’s ten years older’n me. Dad used to make him look after me all the time, if he was out with his drinking mates. This lot came to the house in the night and I woke up. One of them gave me a yogurt to eat. There was another little kid there. A girl. And then we all went out in a car… I didn’t want to go. I felt sick. I was crying but Jimmy belted me.

“And we went to the horse in the dark. Me and the little girl were the only kids. She was howling,” said Jimmy and the skin of his gaunt face seemed to shrink more tightly to his bones as he said it. “Screaming for her mum and he said, ‘Your mum can’t hear you now, she’s gone.’”

“Who said that?” asked Strike.

“Him,” whispered Billy. “The one that strangled her.”

The door opened and a new nurse brought in tea.

“Here we go,” she said brightly, her eager eyes on Strike. The male psychiatrist frowned at her slightly and she withdrew, closing the door again.

“Nobody’s ever believed me,” said Billy, and Strike heard the underlying plea. “I’ve tried to remember more, I wish I could, if I’ve got to think about it all the time I wish I could remember more of it.

“He strangled her to stop her making a noise. I don’t think he meant it to go that far. They all panicked. I can remember someone shouting ‘You’ve killed her!’… or him,” Billy said quietly. “Jimmy said afterwards it was a boy, but he won’t admit that now. Says I’m making it all up. ‘Why would I say it was a boy when none of it ever fucking happened, you’re mental.’ It was a girl,” said Billy stubbornly. “I don’t know why he tried to say it wasn’t. They called her a girl’s name. I can’t remember what it was, but it was a girl.

“I saw her fall. Dead. Limp on the ground. It was dark. And then they panicked.

“I can’t remember anything about going back down the hill, can’t remember anything after that except the burial, down in the dell by my dad’s place.”

“The same night?” asked Strike.

“I think so, I think it was,” said Billy nervously. “Because I remember looking out of my bedroom window and it was still dark and they were carrying it to the dell, my dad and him.”

“Who’s ‘him’?”

“The one who killed her. I think it was him. Big guy. White hair. And they put a bundle in the ground, all wrapped up in a pink blanket, and they closed it in.”

“Did you ask your father about what you’d seen?”

“No,” said Billy. “You didn’t ask my dad questions about what he did for the family.”

“For which family?”

Billy frowned in what seemed to be genuine puzzlement.

“You mean, for your family?”

“No. The family he worked for. The Chiswells.”

Strike had the impression that this was the first time the dead minister’s family name had been mentioned in front of the two psychiatrists. He saw two pens falter.

“How was the burial connected with them?”

Billy seemed confused. He opened his mouth to say something, appeared to change his mind, frowned around the pale pink walls and fell to gnawing his forefinger again. Finally, he said:

“I don’t know why I said that.”

It didn’t feel like a lie or a denial. Billy seemed genuinely surprised by the words that had fallen out of his mouth.

“You can’t remember hearing anything, or seeing anything, that would make you think he was burying the child for the Chiswells?”

“No,” said Billy slowly, brow furrowed. “I just… I thought then, when I said it… he was doing a favor for… like I heard something, after…”

He shook his head.

“Ignore that, I don’t know why I said it.”

People, places and things, thought Strike, taking out his notebook and opening it.

“Other than Jimmy and the little girl who died,” said Strike, “what can you remember about the group of people who went to the horse that night? How many of them would you say were there?”

Billy thought hard.

“I don’t know. Maybe… maybe eight, ten people?”

“All men?”

“No. There were women, too.”

Over Billy’s shoulder, Strike saw the female psychiatrist raise her eyebrows.

“Can you remember anything else about the group? I know you were young,” Strike said, anticipating Billy’s objection, “and I know you might have been given something that disoriented you, but can you remember anything you haven’t told me? Anything they did? Anything they were wearing? Can you remember anyone’s hair or skin color? Anything at all?”

There was a long pause, then Billy closed his eyes briefly and shook his head once, as though disagreeing firmly with a suggestion only he could hear.

“She was dark. The little girl. Like…”

By a tiny turn of his head, he indicated the female doctor behind him.

“Asian?” said Strike.

“Maybe,” said Billy, “yeah. Black hair.”

“Who carried you up the hill?”

“Jimmy and one of the other men took turns.”

“Nobody talked about why they were going up there in the dark?”

“I think they wanted to get to the eye,” said Billy.

“The eye of the horse?”

“Yeah.”

“Why?”

“I don’t know,” said Billy, and he ran his hands nervously over his shaven head. “There are stories about the eye, you know. He strangled her in the eye, I know that. I can remember that, all right. She pissed herself as she died. I saw it spattering on the white.”

“And you can’t remember anything about the man who did it?”

But Billy’s face had crumpled. Hunched over, he heaved with dry sobs, shaking his head. The male doctor half rose from his seat. Billy seemed to sense the movement, because he steadied himself and shook his head.

“I’m all right,” he said, “I want to tell him. I’ve got to know if it’s real. All my life, I can’t stand it anymore, I’ve got to know. Let him ask me, I know he’s got to. Let him ask me,” said Billy, “I can take it.”

The psychiatrist sat slowly back down.

“Don’t forget your tea, Billy.”

“Yeah,” said Billy, blinking away the tears in his eyes and wiping his nose on the back of his sleeve. “All right.”

He took the mug between his bandaged hand and his good one, and took a sip.

“OK to continue?” Strike asked him.

“Yeah,” said Billy quietly. “Go on.”

“Can you remember anyone ever mentioning a girl called Suki Lewis, Billy?”

Strike had expected a “no.” He had already turned the page to the list of questions written under the heading “Places” when Billy said:

“Yeah.”

“What?” said Strike.

“The Butcher brothers knew her,” said Billy. “Mates of Jimmy’s from home. They did a bit of work round the Chiswells’ place sometimes, with Dad. Bit of gardening and help with the horses.”

“They knew Suki Lewis?”

“Yeah. She ran away, didn’t she?” said Billy. “She was on the local news. The Butchers were excited because they seen her picture on the telly and they knew her family. Her mum was a headcase. Yeah, she was in care and she ran away to Aberdeen.”

“Aberdeen?”

“Yeah. That’s what the Butchers said.”

“She was twelve.”

“She had family up there. They let her stay.”

“Is that right?” said Strike.

He wondered whether Aberdeen had seemed unfathomably remote to the teenage Butchers of Oxfordshire, and whether they had been more inclined to believe this story because it was, to them, uncheckable and so, strangely, more believable.

“We’re talking about Tegan’s brothers, right?” asked Strike.

“You can see he’s good,” Billy said naively over his shoulder, to the male psychiatrist, “can’t you? See how much he knows? Yeah,” he said, turning back to Strike. “She’s their little sister. They were like us, working for the Chiswells. There used to be a lot to do in the old days, but they sold off a lot of the land. They don’t need so many people anymore.”

He drank some more tea, the mug in both hands.

“Billy,” said Strike, “d’you know where you’ve been since you came to my office?”

At once, the tic reappeared. Billy’s right hand released the warm mug and touched his nose and chest in quick, nervous succession.

“I was… Jimmy doesn’t want me to talk about that,” he said, setting the mug clumsily back on the desk. “He told me not to.”

“I think it’s more important you answer Mr. Strike’s questions than worry about what your brother thinks,” said the male doctor, from behind Strike. “You know, you don’t have to see Jimmy if you don’t want to, Billy. We can ask him to give you some time here, to get better in peace.”

“Did Jimmy visit you where you’ve been staying?” Strike asked.

Billy chewed his lip.

“Yeah,” he said at last, “and he said I had to stay there or I’d cock everything up for him again. I thought the door had explosives round it,” he said, with a nervy laugh. “Thought if I tried to go out the door I’d explode. Probably not right, is it?” he said, appearing to search Strike’s expression for a clue. “I get ideas about stuff sometimes, when I’m bad.”

“Can you remember how you got away from the place you were being kept?”

“I thought they switched off the explosives,” said Billy. “The guy told me to run for it and I did.”

“What guy was this?”

“The one who was in charge of keeping me there.”

“Can you remember anything you did while you were being kept captive?” Strike asked. “How you spent your time?”

The other shook his head.

“Can you remember,” said Strike, “carving anything, into wood?”

Billy’s gaze was full of fear and wonder. Then he laughed.

“You know it all,” he said, and held up his bandaged left hand. “Knife slipped. Went right in me.”

The male psychiatrist added helpfully:

“Billy had tetanus when he came in. There was a very nasty infected gash on that hand.”

“What did you carve into the door, Billy?”

“I really did that, then, did I? Carved the white horse on the door? Because afterwards I didn’t know if I really did that or not.”

“Yeah, you did it,” said Strike. “I’ve seen the door. It was a good carving.”

“Yeah,” said Billy, “well, I used to—do some of that. Carving. For my dad.”

“What did you carve the horse onto?”

“Pendants,” said Billy, surprisingly. “On little circles of wood with leather through ’em. For tourists. Sold them in a shop over in Wantage.”

“Billy,” said Strike, “can you remember how you ended up in that bathroom? Did you go there to see someone, or did somebody take you there?”

Billy’s eyes roamed around the pink walls again, a deep furrow between his eyes as he thought.

“I was looking for a man called Winner… no…”

“Winn? Geraint Winn?”

“Yeah,” said Billy, again surveying Strike with astonishment. “You know everything. How do you know all this?”

“I’ve been looking for you,” said Strike. “What made you want to find Winn?”

“Heard Jimmy talking about him,” said Billy, gnawing at his nail again. “Jimmy said Winn was going to help find out all about the kid who was killed.”

“Winn was going to help find out about the child who was strangled?”

“Yeah,” said Billy, nervously. “See, I thought you were one of the people trying to catch me and lock me up, after I saw you. Thought you were trying to trap me and—I get like that, when I’m bad,” he said hopelessly. “So I went to Winner—Winn—instead. Jimmy had a phone number and address for him written down, so I went to find Winn and then I got caught.”

“Caught?”

“By the—brown-skinned bloke,” mumbled Billy, with a half-glance back at the female psychiatrist. “I was scared of him, I thought he was a terrorist and he was going to kill me, but then he told me he was working for the government, so I thought the government wanted me kept there in his house and the doors and windows were wired with explosives… but I don’t think they were, really. That was just me. He probably didn’t want me in his bathroom. Probably wanted to get rid of me all along,” said Billy, with a sad smile. “And I wouldn’t go, because I thought I’d get blown up.”

His right hand crept absently back to his nose and chest.

“I think I tried to call you again, but you didn’t answer.”

“You did call. You left a message on my answering machine.”

“Did I? Yeah… I thought you’d help me get out of there… sorry,” said Billy, rubbing his eyes. “When I’m like that, I don’t know what I’m doing.”

“But you’re sure you saw a child strangled, Billy?” asked Strike quietly.

“Oh yeah,” said Billy bleakly, raising his face. “Yeah, that never goes away. I know I saw it.”

“Did you ever try and dig where you thought—?”

“Christ, no,” said Billy. “Go digging right by my dad’s house? No. I was scared,” he said weakly. “I didn’t want to see it again. After they buried her, they let it grow over, nettles and weeds. I used to have dreams like you wouldn’t believe. That she climbed up out of the dell in the dark, all rotting, and tried to climb in my bedroom window.”

The psychiatrists’ pens moved scratchily across their papers.

Strike moved down to the category of “Things” that he had written on his notebook. There were only two questions left.

“Did you ever put a cross in the ground where you saw the body buried, Billy?”

“No,” said Billy, scared at the very idea. “I never went near the dell if I could avoid it, I never wanted to.”

“Last question,” Strike said. “Billy, did your father do anything unusual for the Chiswells? I know he was a handyman, but can you think of anything else he—?”

“What d’you mean?” said Billy.

He seemed suddenly more frightened than he had seemed all interview.

“I don’t know,” said Strike carefully, watching his reaction. “I just wondered—”

“Jimmy warned me about this! He told me you were snooping around Dad. You can’t blame us for that, we had nothing to do with it, we were kids!”

“I’m not blaming you for anything,” said Strike, but there was a clatter of chairs: Billy and the two psychiatrists had got to their feet, the female’s hand hovering over a discreet button beside the door that Strike knew must be an alarm.

“Has this all been to get me to talk? You trying to get me and Jimmy in trouble?”

“No,” said Strike, hoisting himself to his feet, too. “I’m here because I believe you saw a child strangled, Billy.”

Agitated, mistrustful, Billy’s unbandaged hand touched his nose and chest twice in quick succession.

“So why’re you asking what Dad did?” he whispered. “That’s not how she died, it was nothing to do with that! Jimmy’ll fucking tan me,” he said in a broken voice. “He told me you were after him for what Dad did.”

“Nobody’s going to tan anyone,” said the male psychiatrist firmly. “Time’s up, I think,” he said briskly to Strike, pushing open the door. “Go on, Billy, out you go.”

But Billy didn’t move. The skin and bone might have aged, but his face betrayed the fear and hopelessness of a small, motherless child whose sanity had been broken by the men who were supposed to protect him. Strike, who had met countless rootless and neglected children during his rackety, unstable childhood, recognized in Billy’s imploring expression a last plea to the adult world, to do what grown-ups were meant to do, and impose order on chaos, substitute sanity for brutality. Face to face, he felt a strange kinship with the emaciated, shaven-headed psychiatric patient, because he recognized the same craving for order in himself. In his case, it had led him to the official side of the desk, but perhaps the only difference between the two of them was that Strike’s mother had lived long enough, and loved him well enough, to stop him breaking when life threw terrible things at him.

“I’m going to find out what happened to the kid you saw strangled, Billy. That’s a promise.”

The psychiatrists looked surprised, even disapproving. It was not part of their profession, Strike knew, to make definitive statements or guarantee resolutions. He put his notebook back into his pocket, moved from behind the desk and held out his hand. After a few long moments’ consideration, the animosity seemed to seep out of Billy. He shuffled back to Strike, took his proffered hand and held it overlong, his eyes filling with tears.

In a whisper, so that neither of the doctors could hear, he said:

“I hated putting the horse on them, Mr. Strike. I hated it.”