Hitchens studied the photos carefully. ‘Pretty gruesome.’

‘Where would you say they were taken, sir?’ said Fry.

‘Well, this one is in a mortuary somewhere – not ours, but it could be the Medico Legal Centre in Sheffield. And the next one is certainly a crime scene. The victim has gunshot wounds.’

‘Suicide, according to the caption. What about the other two?’

‘I can’t tell. Not a mortuary, anyway. The lighting’s all wrong.’

‘I agree. But the body has been carefully laid out, so they’re not scene photos either.’

‘What do the captions to these say?’ asked Hitchens.

‘One for the necros.’

‘Jesus.’

‘As you can see, they show a female corpse, but with no signs of violence. It isn’t Audrey Steele, thank God.’

The DI looked at her sharply. ‘You think that’s something to be grateful for?’

Fry looked down, but said nothing.

‘A funeral director’s preparation room,’ said Hitchens. ‘It’s got to be.’

‘Perhaps.’

‘We ought to find out whether Robertson has any connection with Hudson and Slack.’

‘We can do that.’ Fry took the photographs back. ‘Yes, they might have been taken in the preparation room at a funeral director’s, but I’m not convinced. I’m wondering if there might be a similar room in the basement of an Edwardian gentleman’s residence.’

‘A what?’

‘Professor Robertson’s home at Totley.’

‘I see.’ Hitchens began to spin his chair again. ‘Diane, this isn’t evidence. It’s speculation. You need something more substantial.’

‘Well, we also came up with this –’ Fry handed him two pages of closely printed text. ‘It’s an article written by Professor Robertson and published on one of the thanatology websites.’

Hitchens ran his eye over the pages. ‘It looks deadly stuff to me.’

‘I’ve highlighted the relevant paragraphs for you, sir.’

‘So you have.’

Fry watched Hitchens read, and saw the recognition dawn on his face. She hadn’t been sure whether he’d make the connection immediately. He hadn’t listened to the tapes of the phone calls as often as she had. He didn’t know the phrases by heart, the way she did.

But, as she watched him, she knew exactly the words that her DI was reading from Freddy Robertson’s website article.

Wasn’t it Sigmund Freud who said that every human being has a death instinct? Inside every person, the evil Thanatos fights an endless battle with Eros, the life instinct. And according to Freud, evil is always dominant. In life, there has to be death. Killing is our natural impulse. The question isn’t whether we kill, but how well we do it. Without a purpose, the act of death has no significance.

For once, the flashing green light on the answering machine gave Cooper a little surge of pleasure as he walked into his flat. He pressed the button and listened to the recording before he even took his jacket off or paid attention to the cat.

‘Ah, yes,’ said the voice. ‘It’s Robertson here.’

Cooper stopped quite still in the middle of the room. Robertson? Professor Robertson? It must be, yet his voice sounded quite different. He’d lost the heartiness completely. Complacency and smugness had gone. Instead, he sounded weary and dejected. And, somehow, very small.