Perez had been thinking about that. ‘I can’t see how it might have happened. If we’d found the body out there, on the old RAF site, then I’d accept it. A row that blew into something more violent. But according to Sinclair, Henderson was only out of the office for an hour. I can’t see that he’d have had time to drive south and set up the ambush, never mind stage the scene in the marina at Aith. And while he was the kind of man – calm, repressed even – who might have a flash of temper, I don’t think that planning would have been in character at all. He had too much of a conscience.’

‘Unlike the Fiscal.’ Willow grinned. The schoolgirl about to reveal her secret.

‘What do you mean?’

‘I should have been in my office chasing up phone records this morning, but I ended up taking our Rhona out for coffee instead.’

‘Did you now?’ Perez found his response to the detective was becoming more natural.

‘I took her to the Islesburgh Centre.’ Willow grinned. ‘No expense spared.’

‘Not the Fiscal’s natural habitat,’ Perez said.

‘She was all right,’ Willow said. ‘Expansive for her.’

‘And?’

‘She and Richard Grey – known to her as Dickie – were lovers in the dim and distant past. She was, and I quote, one of his serial affairs. It was before his wife ran off with her secret lover, but our Rhona had no conscience at all.’

Perez tried to take this in. ‘Any bearing on the killings, do you think?’

‘I’ve been trying to work out how, but I can’t see it.’ Willow gave in to temptation and went to the counter for lemon-drizzle cake, waved to Perez to ask if he wanted anything. He shook his head. On her return she continued as if there’d been no break. ‘I wondered if Jerry Markham had found out about the affair, if Annabel or Richard had given away our Rhona’s raunchy past. But why would they? Surely Annabel never knew about it. She was only five when it was all happening. And even if Markham had discovered that the Fiscal and Richard Grey had a fling fifteen years ago, what could he possibly do with the information? It hardly turns Rhona Laing into a potential blackmail victim.’

‘No.’ Perez considered how this might relate to the theories spinning around in his head. ‘The only person who’d be hurt by the affair being made public would be Annabel. She obviously dotes on her father and believes in the public persona of respectable family man, given to charitable good work.’

‘And Richard might be hurt too,’ Willow said. ‘Annabel obviously worships him. I imagine that relationship would take a bit of a nosedive if she found out about his sordid past.’