‘I never looked at this,’ she said. ‘It’s spooky.’

‘What’s the MO?’

Carla flicked through a couple of pages. Memories that were years old came immediately to the surface. Her voice was edgy. ‘Chloe was found naked on her bed by her mother. She was posed like a beauty queen or something with her hair all lying out on her pillow, but she had a big cut all the way up her chest. He cut out her heart. It was a botched job. Very messy.’

‘It’s the same MO,’ said Harper faintly.

‘She was covered in flower petals. It happened on Valentine’s Day. Nice touch.’

It was the American Devil all right. The thought was terrifying. A man had started killing some twenty-five years earlier and he was still evading the police.

Harper and Carla talked through the rest of the details for the next half-hour, but the original investigation had got nowhere. In the end they put it down as a passing vagrant. It was anything but a vagrant.

‘What are you looking for, Tom?’ said Carla after they’d exhausted the reports.

‘I don’t know. Anything that might open up an angle here.’

‘Well, I’ll be here if you need me,’ said Carla.

Harper put the phone down. Sebastian had killed before. What did that mean? If Denise’s profile was right and the killer was in his thirties, then even if he was approaching forty that put him around mid-teens in 1982. Was that possible? Could this whole horror story have started as someone’s adolescent fantasy?

Chapter Ninety-Nine

Mace Crindle Plant

December 3, 8.30 p.m.

‘Dr Levene,’ said the strange, contorted voice. Denise jerked her head. He was back, but his voice was different. It wasn’t so deep and full. It was kinder.

‘Are you listening, Dr Levene?’

The way he crept silently into the antechamber worried her. Was he studying her? He might’ve been sitting there for hours watching her. A patch of light hit the floor of her prison.

‘Please, Dr Levene.’

Denise didn’t reply. Not yet. Make him work for it.

‘I want to talk to you.’

Stay composed, Denise.

‘My name’s Nick.’ Nick felt sick in his stomach. He knew how dangerous this was. Sebastian wouldn’t forgive him for intruding. ‘I didn’t know who you were when I found you down here, then I put two and two together. You’re the woman they’re all looking for, aren’t you? You’re in every newspaper. Every one.’

Denise listened. What game was he playing? ‘Where’s Sebastian?’

‘Sebastian hurt my son today.’ Nick hung his head low. ‘Sebastian took a spoon to his eye. He was going to gouge out my son’s eye. I’ve got to stop him.’

‘I don’t understand,’ said Denise.

Nick moved erratically around the room.

‘Please don’t ask any more. I’m not in control of what he does. I can’t stop him. He’s going to kill them all, Dr Levene. He wanted to kill you, but I forced him out. I needed to see you. You can help me. He’s going to starve you in this dungeon and then ...’

‘What?’

‘He wants to use you to get to Tom Harper. I’ve got pictures of him on my phone. That’s how I know. He leaves his victim’s pictures on my phone.’

‘Why does he want Tom Harper?’

‘I don’t know. I just know I can’t stop him.’

‘I don’t understand,’ said Denise. ‘Who are you?’

‘I don’t know,’ said Nick. His voice was low and fearful, with a hint of West Virginia in there somewhere. ‘It’s in the Bible. It’s called demonic possession. He’s evil, Dr Levene, and he’s taking over.’

‘He’s inside your head?’

‘He’s in my head. He’s in my hands. I don’t want him to kill. He’ll kill my family. He knows I tried to stop him. That’s why he went for William, see. If I go home again, he’ll kill the boy. I love my boy, Doctor. I love my boy.’

Nick paused. She couldn’t believe what she was hearing. She couldn’t believe that this was the vicious, sadistic killer responsible for nine deaths. And that he was asking for her help. His voice was so soft and considered that it was difficult to imagine that it could belong to a killer.

‘If you’ve got some kind of multiple personality disorder,’ she said, ‘I can try to help you,’

‘How can you help me, Dr Levene? I’ve tried with psychologists. I’ve tried, but no one can stop him.’

‘We can try, Nick,’ she said. She had no idea what she was intending to do. She was just looking for something that gave her some control. ‘I can try some things with you, if you want me to ...’

‘If you can stop him, Dr Levene. If you can stop him killing my children.’

‘Yes,’ said Denise. ‘But you have to understand, you want to think he controls you, but he doesn’t. You control Sebastian, Nick, you just don’t realize it. Please, sit down, let me talk to you.’

Nick sat without another word and listened to the doctor.

Chapter One Hundred

Mace Crindle Plant

December 3, 9.00 p.m.

In a dungeon forty feet below Manhattan, an old pump room with brick walls was about to witness a bizarre experiment. Nick was going to undergo CBT. Denise was going to alter his behaviour - at least for long enough to allow her to escape. It had to work. But first they had to trust each other, form an alliance. An alliance against Sebastian. And Denise knew that she needed to convince Nick that it was not about Sebastian, it was about himself. It was Nick who let this fiend take over and control things. In that respect he was no different from a drunk or a violent husband or a depressive.

Denise found her mind twisting between the horror of her situation and the practical truth that the anti-social part of his behaviour needed to be removed from his coping strategies. She was even surprised herself that she could switch so easily from a horrified victim to a doctor.

Nick stayed in his seat. Denise was hooded but free to move around. She needed to move to think.

Nick sat patiently and expectantly. In his eyes, she - like Marty before her - was his only hope of escaping this vicious cycle of murder and guilt. He was nervous, though. Anxious about the treatment and afraid because Sebastian would punish him for letting her do this.

She started by trying to find the words, trying to formulate a way forward. It was hard. The circumstances were so strange that she was close to shrieking, but she didn’t. She opened her mouth and let the routine come out all of its own accord.

‘What this is called, Nick, is cognitive behavioural therapy. What we’ve got to do is identify the problem we have. I don’t want to know about your childhood or any internal feelings, I just need to know which actions and behaviour you find unacceptable.’

‘He murders people, Dr Levene! I want to stop him hurting people!’ Nick shouted and then hid his face in his hands, ashamed of his weakness.

‘What we have to do is to discover the nature of the problem in terms of the pattern inside your head. The relationships between how you feel, what you think and what you do. Do you understand that? Feel-think-do. We’ve got to look closely at these things.’

Nick stayed silent. He was thinking. Feel-think-do - that was Sebastian all over. He felt the urge, he thought about it and then he killed. Feel-think-do.

‘We will agree goals for you and a method of identifying trigger feelings and trigger words, then we will find a simple physical way to re-programme your behaviour. That sound okay?’

‘Yes.’

She breathed deeply. This was a journey into the unknown. She knew that CBT had been successful even in cases of extreme schizophrenia, so why not with this guy?

Denise’s hunch was that Nick had called on Sebastian early in his life when he needed help to cope with some painful trauma that had made him feel so weak and useless that he basically collapsed inside. Sebastian had been a saviour at some point - a friend, someone who supported Nick and gave him strength. But when strange demonic urges started entering Nick’s head, Sebastian was there to take the blame. Then, at some point, Sebastian had started living an independent existence.