For all of which, the process control room was about as peaceful a place as Rebus had ever been. Two men and a woman sat behind computer consoles in the centre of the room, while the walls were taken up with electronic charts, softly flashing lights indicating the oil and gas flows. The only sounds were those of fingers on keyboards, and the occasional muted conversation. Walt had decided that it was his job to introduce Rebus. The atmosphere had quieted him, as if he’d walked into the middle of a church service. He went to the central console and spoke in an undertone to the trinity seated there.

The elder of the two men stood up and came to shake Rebus’s hand.

‘Inspector, my name’s Milne. How can we help?’

‘Mr Milne, I really wanted to speak to Jake Harley. But since he’s made himself scarce, I thought maybe you could tell me a little about him. Specifically, about his friendship with Allan Mitchison.’

Milne wore a check shirt, its sleeves rolled up. He scratched at one arm while Rebus spoke. He was in his thirties, with tousled red hair and a face pitted from teenage acne. He nodded, half-turning to his two colleagues, assuming the role of spokesman.

‘Well, we all work beside Jake, so we can tell you about him. Personally, I didn’t know Allan very well, though Jake introduced us.’

‘I don’t think I’ve ever met him,’ the woman said.

‘I met him once,’ the other man added.

‘Allan only worked here for two or three months,’ Milne went on. ‘I know he struck up a friendship with Jake.’ He shrugged. ‘Really, that’s about it.’

‘If they were friends, they must have had something in common. Was it bird-watching?’

‘I don’t think so.’

‘Green issues,’ the woman said.

‘That’s true,’ Milne said, nodding. ‘Of course, in a place like this, we always end up talking about ecology sooner or later – sensitive subject.’

‘Is it a big thing with Jake?’

‘I wouldn’t go that far.’ Milne looked to his colleagues for support. They shook their heads. Rebus realised that nobody was talking much above a whisper.

‘Jake works right here?’ he asked.

‘That’s right. We alternate shifts.’

‘So sometimes you’re working together …’

‘And sometimes we’re not.’

Rebus nodded. He was learning nothing; wasn’t sure he’d ever actually thought he would learn anything. So Mitchison had been into ecology – big deal. But it was pleasant here, relaxing. Edinburgh and all his troubles were a long way away, and felt it.

‘This looks like a cushy job,’ he said. ‘Can anyone apply?’

Milne smiled. ‘You’ll have to hurry, who knows how long the oil will last?’

‘A while yet surely?’

Milne shrugged. ‘It’s down to the economics of retrieval. Companies are beginning to look west – Atlantic oil. And oil from west of Shetland is being landed at Flotta.’

‘On Orkney,’ the woman explained.

‘They won the contract from us,’ Milne went on. ‘Five or ten years from now, the profit margin may be bigger out there.’