‘If it’s the same killer, he clearly isn’t able to take the women home. That suggests he’s got someone at home that he needs to hide this from. Your unsub is probably in a long-term relationship, Captain. Not a good sign if he’s used to hiding his activities from a family and a job, because he’s going to be good at this. He’s in it for the long haul and wants to keep clean. He might have brought her here because of the water. The press reports mentioned fibres found on Mary-Jane’s body, so maybe he’s just making sure he doesn’t make the same mistake twice. Maybe he knows about police procedure.’

‘You think he’s cleaned her?’

‘I think it’s possible, yeah. Possibly more than that. I don’t know yet. He’s also carrying something. Not sure what, but my guess is that it’s a camera and tripod. He’s playing games, deep inside his head, and he’s working up to something. The posing is getting more explicit. I think the killer is getting to like this.’

‘You got more in fifteen minutes than Williamson had in a week.’

‘You’re trying all the tricks, aren’t you?’ said Harper. ‘I said I’d take a look, I took a look. Am I free to go now?’

‘Is that what you want? A dismissal, criminal charges and a job with a security firm?’ Harper stared out of the car in silence. ‘I can make the charges go away, Harper, but . . .’

‘But what?’

‘But, Harper, you’re also considered unstable. You agree to come back on the team, I’ll make it happen, but you gotta see someone to help you through the stuff in your head. Don’t be a tough guy: you need help. I can smell the drink on your breath and read the signs and it’s not a path you want to take. See someone - see a shrink, someone to talk to.’

Harper’s hand clenched involuntarily. He held his breath for a moment, looking down into the footwell of the car. ‘I don’t think I can, sorry. I’ll take my chances.’

Lafayette reached across and put his hand on Harper’s shoulder. ‘Don’t let her kill you, Tom. It’s her life, she made her choices - don’t be a fucking reaction the rest of your days.’

Harper got out of the car. He leaned down and looked in at the captain. ‘One more thing.’ He held up a small pink petal. ‘This is cherry blossom. Ask the question - where the hell did he get cherry blossom in November?’

Chapter Five

Barnard College

November 16, 2.59 p.m.

Dr Denise Levene walked up the steps to the small podium in Held Lecture Hall at Barnard College, right across the street from Columbia University. She didn’t often do public lectures since taking up a position with the NYPD, where she offered CBT to disturbed cops.

The audience of 150 was a mix of students and anyone who cared to drop in. They applauded the arrival of the research scientist with dutiful enthusiasm. Dr Levene looked out at the expectant faces. The glare of the stage lights blanked out their features. She never really enjoyed public speaking. She was happiest in the security of her lab working with her taciturn research students. Still, that didn’t mean she didn’t know how to put on a good show.

Denise smiled at her host, then raised her hand, and the audience hushed. ‘Thank you. Thanks for coming.’ Her hand moved to the control on her podium. She set her DVD in motion.

In the audience, a striking-looking man in a black suit and a beige mac, his neck low in his collar, was staring intently at Dr Levene. He was bored of waiting. He was often bored. He cursed under his breath and then, under the bench, he took a two-inch pocket knife and pushed it through his pocket lining and about a quarter of an inch into his thigh. Denise Levene was supposed to be an expert on the causes of violence. What would she make of him? He was eager to know.

All the man in the black suit wanted answered was why - he wasn’t after a cure, for Christ’s sake, just a little bit of an indication of what he was. An idea. A notion. He twisted the knife in his thigh, opening the wound. He watched his own body’s reaction to the pain. It was just a phenomenon in his head. No need to react, no need to give way to the urgency of biology. He had always felt more than that - more than merely human. He was sanctioned by his own pain to hurt anything and anyone.

What was pain, anyway? Just a neurological electro-chemical pulse, not a real thing at all. A chimera, like love, like happiness, like life. Like goodness. He looked across at the audience. Scientists were so slow. He yawned and tapped his fingers in agitation.

‘What you are about to see, ladies and gentlemen,’ said Dr Levene, ‘is a journey to the cause of human intraspecies violence.’

‘About time,’ murmured the man in the black suit.

The audience looked up at a large brain scan. The two great hemispheres of a single brain were projected on to a forty-foot-high screen.

‘The following sequence is a brain scan of a child who is in the process of learning.’

On the screen, the brain danced with colour in different areas - reds, blues, golds. Connections sparking and fading at incredible speed. It was like a New Year light show.

‘The brain is a learning tool,’ she continued. ‘It is the one thing in which we excel over other species - the capacity to learn: we are the pre-eminent learning animal. For a long time, scientists presumed that the brain came pre-packaged at birth, like a computer preloaded with software that you just had to switch on. We now know that the brain comes pre-packed but very empty. No software installed, just the bare components. Life is our software, ladies and gentlemen; we write the code as we walk, eat and breathe. And each of us writes a different code.’

She clicked her mouse button and the next video streamed in. ‘What you can see here is the growth of a single brain neuron. At birth, we have all of our billions of neural cells. But the brain is not the function of these cells alone. The brain - what we know as our consciousness - is formed out of life’s experience, out of the experiences that make up every second of our life. Watch this single neuron get to work.’

The image of the small elongated cell began to shake slightly and small branches started to reach out from its sides and from both ends. Soon these branches were branching in their turn and suddenly, out of the darkness of the screen, they were connecting with branches from other nearby cells that became illuminated.

‘You are watching human thought in action, ladies and gentlemen. The single neuron has the capacity to make a million connections. You have a billion neurons. That’s a lot of connections. And these connections are made through experience and thought. But today I want to tell you about my research into “non-thought” - the experience of the “unlit” zone.’

She clicked again and the single neuron returned to its pre-thinking state, a single isolated cell in the middle of a field of darkness.

‘See this cell: it knows nothing of what’s around it. Its relationship to the world is non-existent. It does not know what’s out there. How do we, as human beings, experience this darkness in our own minds? Why do these dark areas matter?’

Denise thought it was going reasonably well. Some faces seemed genuinely interested. She clicked again. ‘This is the brain scan of a child who has suffered serious neglect between the ages of zero and three. I think that you’ll find it quite interesting.’

The slide came up. A gasp of fascination rippled through the assembled crowd. The scan showed a neural network with a dark hole in the centre.

‘In circumstances of serious abuse and neglect, the brain does not form correctly, and vast areas remain unconnected - like unexplored regions. What this means is that for some abused or neglected individuals, there is simply no connection between the parts of the brain that create normal behaviour. Some people do not have the mental capacity for empathy, control of impulse or fear of consequence - the roads simply don’t go there.’