Cooper knew that suicide was often an act of anger against people who were close to the victim but had failed to recognize their despair. Or it could be aimed at those who caused the despair in the first place. In its way, suicide was an especially cruel form of revenge.

But Fry looked unconvinced. He guessed she might be remembering the words of one of the phone messages: As a neck slithers in my fingers like a sweat-soaked snake … They would never know whether Vernon had been referring to a real killing or re-living a fantasy. Was that what he’d been thinking as he sat in the wrecked van with his father helpless at the wheel? It was a moment when he might have acted out his fantasy of killing the man he hated.

‘You know Vernon Slack studied under Professor Robertson?’ said Fry. ‘He was the professor’s star student, apparently.’

‘So he’s not quite as dumb as he seems.’

Cooper paused, letting the sentence repeat in his head. It seemed to be accompanied by faint and unidentifiable music.

‘Isn’t that a line from a song?’

‘Damn, you’re right,’ said Fry. ‘What is it?’

‘I can’t remember. But it’ll come back to me later on, when I’m not thinking about it.’

‘I hope so. Otherwise it’s going to keep going through my head for the rest of the day.’

Cooper stood up with some difficulty, trying not to show too much discomfort. ‘You know,’ he said, ‘I think Freddy Robertson would consider a star student to be the person who took in every precious word and echoed his own views most faithfully.’

‘Yes, you’re right, Ben. I bet he liked Vernon because he was easy to influence. Faithful is a good word. And loyal, too – like a dog.’

‘Why do you say that?’

‘Well, he’d kept the professor’s secrets for a long time. He stayed loyal, even when Robertson himself started to worry that Vernon would crack and give him away.’

Cooper frowned. ‘Is that the way you read it?’

‘What do you mean, Ben?’

‘I think the loyalty was the other way round. Vernon thought he was doing Robertson a great service by obtaining a real body for him. It was meant to be a special gift, the way a cat brings its kill into the house for its owner.’

‘Are you talking about Audrey Steele?’

‘Yes, of course. The theft of her body was nothing to do with Richard Slack – it was Vernon’s idea. But Robertson rejected his offering. It was a step too far for the professor – it brought death a little bit too close. Perhaps he was completely horrified by the idea.’

‘So he was nothing but talk, after all.’

‘But he didn’t give Vernon away, did he?’ said Cooper. ‘That’s what I meant about loyalty.’

‘How do you know all this, Ben?’

He slid a plastic evidence bag across the kitchen table. It contained an exercise book with a red cover, the pages well thumbed and loose. The outside of the bag was stained with a streak of blood. Cooper realized the blood was probably his own.