‘I just mean that they were similar in lots of ways, and that made their relationship difficult.’

‘They argued?’

‘It was more that they couldn’t let an argument lie. There had to be a winner and a loser, no middle ground.’

‘Did these disagreements ever turn violent?’

‘No.’

‘But David’s got a temper on him?’ Rebus persisted.

‘No more so than anyone else.’

Rebus walked over to the table. It only took him a couple of steps. He leaned forward so that his shadow covered Winfield. ‘But you’ve seen him lose the rag?’

‘Not really.’

‘No?’

Siobhan cleared her throat, a sign that she thought Rebus had hit a wall. ‘Albert,’ she said, her voice like a balm, ‘did you know that Flip liked to play computer games?’

‘No,’ he said, looking surprised.

‘Do you play them?’

‘I used to play Doom in first year … maybe pinball in the student union.’

‘Computer pinball?’

‘No, just pinball.’

‘Flip was playing a game online, a sort of variation on a treasure hunt.’ Siobhan unfolded a sheet of paper and slid it across the table. ‘Do these clues mean anything to you?’

He read with a frown, then expelled some air. ‘Absolutely nothing.’

‘You’re studying medicine, aren’t you?’ Rebus interrupted.

‘That’s right. I’m in my third year.’

‘I bet it’s hard work,’ Siobhan said, sliding the sheet of paper back towards her.

‘You wouldn’t believe it,’ Winfield laughed.

‘I think we might,’ Rebus said. ‘In our line of work, we see doctors all the time.’ Though some of us, he could have added, do our best to avoid them …

‘I’m assuming you know something of the carotid artery then?’ Siobhan asked.

‘I know where it is,’ Winfield admitted, looking puzzled.

‘And what it does?’

‘It’s an artery in the neck. Actually, there are two of them.’

‘Carrying blood to the brain?’ Siobhan said.

‘I had to look it up in a dictionary,’ Rebus told Winfield. ‘It’s from the Greek, meaning sleep. Know why that is?’

‘Because compression of the carotid causes you to black out.’

Rebus nodded. ‘That’s right, a deep sleep. And if you keep on pressing …’

‘Christ, is that how she died?’

Siobhan shook her head. ‘We think she was rendered unconscious, then strangled afterwards.’

In the silence that followed, Winfield looked wildly from one detective to the other. Then he started rising to his feet, fingers gripping the table’s edge.

‘Jesus Christ, you don’t think … ? For pity’s sake, you think it was me?’

‘Sit down,’ Rebus ordered. In truth, Winfield hadn’t got very far up; it looked like his knees were refusing to lock.

‘We know it wasn’t you,’ Siobhan said firmly. The student fell back on to his chair, nearly toppling it.

‘We know it wasn’t you because you’ve got an alibi: you were with everyone else in the bar that night, waiting for Flip.’