‘Ah.’ He leaned forward across the table. ‘That’s the important question, isn’t it?’

‘To Evie Watt, do you think?’ Willow found herself groping towards an explanation. ‘Perhaps she did meet Markham in the Bonhoga, after all. Perhaps he passed on information. Something he’d discovered in his research.’ Suddenly she was excited. She could feel the possibility that she might connect all these unrelated strands of the investigations. ‘His story. The story that brought him to Shetland in the first place. Something to do with her work? The green energy? The Fiscal was on the working party for the tidal-power project. The Power of Water. Perhaps that’s the reason Markham’s body was left on the water at Aith. Another message. To a twisted mind. And Markham met Henderson too, perhaps looking for more information, or giving it. And the postcard is a message to Evie to keep her mouth shut. What do you think, Jimmy?’

She could tell he was considering the theory, running through the facts in his head. ‘Yes,’ he said. ‘Yes, it could have worked that way.’ She thought he seemed almost relieved. She wanted to ask him what weird and dreadful scenario he’d conjured up. Why is my theory so much more attractive to you? But she was a detective and not a shrink, and she was exhilarated because all these disparate facts were finally hanging together. So instead she concentrated on actions for the day.

‘I’d like to see Joe Sinclair.’ She looked at Perez. ‘He was on the working party with Rhona Laing and Evie, but not a suspect in any way that I can see. An impartial witness. And I’d like to see the site for the tidal-energy project. He could talk me through it, couldn’t he? All the technical stuff?’

Perez hesitated for a moment and then nodded.

‘I was thinking I’d take Sandy with me,’ she went on. ‘Let him out of the office for a while.’ And there’s no way I can put up with your moods today.

Perez nodded again. She stood up, irritated by his silence.

‘Would you mind if I spoke to Rhona?’ he asked. She was on her way out and she had to turn to look at him. ‘I know you saw her yesterday, but she left a message on the answer phone the evening before. Wanting to talk to me. You wouldn’t mind?’

She froze, her hand on the door, revisited by the old suspicion that Rhona and Perez might be colluding over some part of the investigation. But if that was the case, Perez had no need to ask her permission before talking to the woman. He could just have picked up the phone. At least now he was keeping her informed.

‘Of course, Jimmy. But don’t give her any details. Nothing about the postcard or these recent ideas. I don’t have to tell you that.’