‘Anything mechanical is unalive, and therefore predictable and reliable. If a machine breaks down, you can figure out why, and repair it. But people aren’t like that. We can’t always understand why they behave the way they do.’

‘That’s certainly true of some people around here,’ said Murfin. But Dr Kane ignored him. She’d probably noticed that Murfin hadn’t opened his notebook. Chances were he didn’t even have a pen with him.

‘For a subject with this type of personality disorder,’ she said, ‘machines are vastly preferable. If they’re forced to deal with people, that’s when problems can arise. Human unpredictability appears threatening. A subject may feel the compulsion to render a living person unalive, to make them safe.’

That was too much. Fry felt the irritation boil over.

‘Render a person unalive? What sort of mealy-mouthed expression is that?’

Kane paused, pursed her lips and brushed back a strand of hair. She was silent for just long enough to make it clear she wasn’t going to respond to the question. She looked up at DI Hitchens.

‘In terms of an individual’s own distorted perceptions, such an act might be considered a form of self-defence,’ she said.

Fry snorted, and Hitchens glared at her.

‘There’s another thing that might help you,’ said Kane. ‘Personality disorders of this nature often become evident in childhood. But it generally requires some kind of traumatic experience to bring it to the surface, producing a child who clings to ritual as a source of security. Such a child will find predictability reassuring, even when it flies in the face of normal logic.’

‘Can you give us an example?’ asked Hitchens.

‘Imagine that you’re a child, and your father sometimes beats you when he comes home drunk on a Saturday night. A normal child will keep his head down and hope his father won’t beat him this week. But if you’re this kind of child, it’s preferable for your father to beat you every Saturday night, rather than not knowing whether he will or won’t. Unpredictability is the most frightening thing, you see. A child in that situation might deliberately do something to enrage his father, to make sure that he’s beaten. Then he feels secure.’

‘Good God.’

Kane nodded. ‘It’s a difficult disorder to deal with. There are no cures, only ways of minimizing the effects – and then only if the condition is diagnosed before it’s too late.’

‘Too late?’ said Hitchens.

‘Well, as a child, this type of individual lacks the power to influence the actions of adults, other than by making himself a victim. But later in life he may realize there’s another way to deal with the unpredictability of people.’ The psychologist turned her head slightly to look at Fry. ‘That’s when he discovers the power to make them predictable – by rendering them unalive.’