Perez looked at him. Earlier in the week he’d thought Sandy had matured. The man had dealt with Gwen James with sensitivity, come back with more information about Hattie than Perez had expected. Now he was like a toddler throwing a tantrum over a lost toy, blaming his parents for his misery.

Sandy met his eye. He must have realized how disappointed Perez felt because his tone changed. ‘OK, I’ll phone them.’

Perez carried the coffee cups into the kitchen. Through the wall he heard Sandy’s muffled voice, still defensive and angry, but he couldn’t make out the words. When he returned to the room the conversation was over. He drew the curtains and waited for Sandy to speak. That was why the man was here, after all. Why else would he have turned up on the doorstep in such a state?

‘My parents are going to sell Setter,’ Sandy said.

Perez nodded. ‘It makes sense. They wouldn’t want to leave the house standing empty, and doesn’t Joseph work most of the croft anyway?’

‘You don’t understand. My father doesn’t want to sell. He hates the idea. He didn’t even want the dig to go ahead. And now there’s this grand do in the hall. Mother says it’s about showing folk the coins found on the land, but it’ll be about persuading the Trust to buy the house. If the sale goes ahead, they’ll be digging up all over the land, maybe even knocking down Mima’s house to put up some sort of replica. And my father just says, “Fine, go ahead.”’

‘What are you worried about, Sandy? I don’t really see the problem. It’s your parents’ house now. Their decision.’

‘I want to know why he changed his mind.’ It came out as a shout, so loud that Perez thought the neighbours would hear through the wall. ‘He’s not a man to change his mind.’

Perez sat still and waited for the rest.

‘Someone’s put pressure on him,’ Sandy said. His voice was quieter but still intense.

‘Your mother, maybe. She’s a woman used to getting her own way. Nothing sinister in that. You know how excited she is about the history.’

‘Not my mother. She’s all bluster and talk, but he takes the decisions in the house.’

‘What then?’

‘Blackmail,’ Sandy said. ‘I wondered if that could be it. He needs the money to pay someone off.’ He looked at Perez, desperate to be told that it was a crazy idea. He was Sandy Wilson and he got everything wrong.

But Perez didn’t speak for a moment. He was considering the possibility seriously. The scenario he’d dreamed up to explain the Whalsay deaths didn’t involve blackmail, but perhaps it could fit in with the facts. At this point anything was possible.