Harper started to pick his way towards the body. He reached the rock as Hernandez’s light flashed across her face. The light from the officer on the right spread out across her side. It was a horrific sight. She was a young woman in her early twenties. Her skin was white as alabaster. Her naked body lay flat on its back, her hands wired together on her chest as if in prayer, her legs raised and spread wide apart. Her feet and ankles had been jammed into two rock crevices. All over, wet petals stuck to her skin and the rock. Harper picked one up from the rock and turned it in his hand.

He looked closely at the body, careful not to touch or move anything that might be evidence. He was working out the sequence, trying to spot the small things that didn’t quite fit. The woman’s hair was short and scruffy, her face thin, with well-defined cheekbones. Harper leaned in and looked more closely. His flashlight moved slowly over the corpse. Ten minutes was all he gave himself. He knew he didn’t have long before the coroner arrived to take the body off the rocks, so he pulled himself back up to the bank. He stood and faced the two officers who hadn’t moved. ‘Why are you still hanging around here? Haven’t you got something to do?’

‘Before we take orders, let’s see your shield, Detective,’ said Cob with a sneer. ‘You ain’t got no ID showing. Maybe you ain’t a detective at all.’

Harper turned to the poor woman who’d been executed on the cold rock, probably screaming her lungs out where no one could hear. The killer didn’t have any human feelings at all and now Officer James Cob wanted to bust his balls.

Harper walked across to Cob and stood face to face. ‘You want to know who I am?’

‘Yeah, and what you’re doing here.’

‘And what I’m doing here, is that right?’

‘Yeah. You’re so quick, you should be a detective.’

‘I’m nobody but I’m here to find out why this woman was attacked.’ Harper felt his back teeth lock together.

‘Personally,’ said Cob, ‘I’d say she was asking for it, going out dressed like that. She ought to wear a little more, wouldn’t you say?’

‘You think, do you?’

‘She ain’t got much on,’ said Cob.

‘You want to know what it feels like to be down on those rocks, Officer?’ Harper reached, quick as a rattlesnake, and snapped his big hand round Cob’s wrist. His eyes stared hard.

‘Get the fuck off me!’ Cob shouted.

‘You think it’s funny that a woman’s been raped and executed?’

‘No. I was ... Come on . . .’

Harper pulled Cob’s arm hard and shoved him down towards the corpse, flicking his leg across the officer’s weight. Cob fell hard on to the muddy bank, a look of stark panic on his face. He was badly winded and Harper still had his wrist in a vice-like grip.

‘Doesn’t feel like you’re sorry, Cob.’ Harper dragged Cob towards the edge of the bank.

‘What the fuck are you doing, you madman?’

‘Have a look at her face, Cob. Do you think it’s funny? Do you think it’s funny what he did? Look at her, you animal.’

Cob, with his face in the cold dirt, stared down at the result of hatred and violence jammed on the rock.

‘You think your girlfriend or mother would think this is so fucking amusing?’

‘Please, man.’

‘How fucking sorry are you, Cob?’

‘Very sorry. Very, very sorry.’

Harper released Cob. ‘Don’t ever talk like that about a victim, you asshole.’ He twitched and strode off over the grassy bank, taking huge strides, his black coat flapping behind him.

Cob rose from the mud, his back sodden, his wrist aching. He looked at the three officers, Hernandez ankle deep in water, Lees pale at the edge, Poulter back down from his vantage point.

‘You fucking nutcase, Cob,’ said Poulter.

‘What? Who the fuck was that guy?’

‘You don’t know? That was Tom Harper.’

‘What’s his problem?’

‘Oh, there ain’t just one. Everything’s his fucking problem,’ said Poulter.

Harper’s silhouette disappeared over the brow of the incline, leaving the rest to North Manhattan Homicide to clear up and assess. He had what he needed. There was a dead woman on his ground. A young woman raped and murdered for no reason. This was not a random strike - the killer had chosen a defenceless victim simply because she was weak. It wasn’t fear that was knocking against Harper’s heart now, it was cold determination.

As he walked, the trickle of images was already forming. Harper’s mind worked like a hundred cogs, assessing information and throwing out conclusions. He figured that the attacker had come at her from behind. A sign of his weakness. He’d taken her out with a blackjack; it’d left a three-inch gash on the side of her head. He didn’t even have to struggle with any resistance. Then he’d somehow got her to his car and driven her out to Ward’s. From the road, he’d dragged her to the rocks, raped her while she was still out, then cut her open and watched her begin to die. Finally, he strangled her.

Harper reached the top of the hill. He turned and looked down. The body had been dragged across the ground. Harper followed the line in the grass. The girl was maybe 110 pounds, but the line wasn’t true or consistent. Maybe the killer was physically weak. He couldn’t even hump a 110-pound body across the ground without stopping every ten yards. Or he was carrying something and using only one arm to drag her. Harper looked again at the drag marks with his flashlight. Yeah, the killer was carrying something with one arm and dragging her with the other. Scrub weak, this killer was physically strong. Very.

Manhattan Psychiatric Center was only a hundred yards away. A possible link, he thought. Ward’s Island was home to two psychiatric hospitals. Most of New York’s criminally insane were within a mile of this spot.

Harper looked across to the grounds of MPC. Plenty of places to hide. He looked back at the officers on the shore. He let the thought about what he’d do if he found the guy flood his mind. The guy who’d attacked and forced himself on this woman - called her names, shouted at her, made her weep and wet herself and shudder with fear, and then, when she was most terrified, slashed at her with his knife. Slow and painful beyond description. Then there was an act that was strangely redemptive - he scattered petals on her body and put her hands together in prayer. Harper knew why Lafayette had wanted him personally on the case. Killers like this played by different rules.

Harper pulled open the door and got into the Impala. He was thinking, still working out the movements that had been this woman’s last.

‘What you got for me?’ said Lafayette.

‘Victim’s not from the hospital, she’s too high class - she’s got an expensive dye job, perfect nails and enough dental work to set you back twenty thousand. She’s in her early twenties and she’s been well looked after. Her hair’s been hacked off. My guess is that he’s taken her hair as his trophy. Looks like her right shoulder’s been dislocated. So he’s abducted her somewhere in the city and then driven her here. He’s dragged her across the ground by one arm. I’d say that the killer has probably been scoping this area for some time and possibly the victim too. She’s a type. Similar to Mary-Jane. Blonde, refined, wealthy. The killer might even have a reason to be here. I’d say that he’s probably been to and from this hospital many times. He might be a patient or even a nurse. That’s a good spot he’s picked. I think he worked the sightlines. The waterline on the rocks is invisible from beyond this hill. So he’s taken the trouble to get her out of sight so he can spend time with her. That’s some careful working out he’s done. Also, he probably drinks. I’d say he needs to drink before he does this. It’s just a hunch. Check traffic, see if they pulled over any drunk drivers in the last couple of months. He’s tried to make it look like a random attack, but I think this guy’s clever. I think he knew exactly who she was and where he was taking her.