The bathroom was spotless and functional. No candles, no perfume. Only one toothbrush. Evie Watt never slept here, Willow thought. She never stayed over. Then it came to her, almost as a revelation, that the two engaged people had never had sex. They were religious and had decided to wait until they were married. She felt tears in the corner of her eyes and wiped them away with her sleeve, hoping that Perez hadn’t noticed.

It was clear that Henderson had slept in the smaller bedroom. It was at the back of the house. No view, except of a bare hillside. A single bed, made up the old-fashioned way with sheets, blankets and a quilt. On the bedside chest a Bible and a pamphlet of suggested religious readings and thoughts. A photograph on the wall of a group of men in uniform next to a sparkling new boat. One of the Sullom Voe tugs? Willow recognized John Henderson standing in the middle. Still there was no indication that anyone had broken into the house and stabbed him to death.

Willow turned back to Perez. ‘What do you think?’ His silence was beginning to irritate her.

He shrugged and moved back to the hall. Here the floor was laminate, and a steep wooden staircase, almost a ladder, led up into the loft. This time he went ahead of her. Perez clambered inside, then moved away from the top of the steps so that Willow could follow. The loft covered the whole house, and dormer windows let in light and gave a view right along the coast. There were no straight walls and Perez could only stand upright in the middle of the room. It was as if she’d walked into a different universe. The walls were painted red. A double mattress on the floor was covered with an Indian cotton cloth in patterned reds and gold. Posters advertising concerts, a festival called Wordplay and the Tall Ships Race were fixed to the slanting walls.

‘What is this place?’ Willow said. ‘Evie’s space, do you think? Is this like the polytunnel and the wind turbine? Henderson’s attempt to woo her? To show that she wouldn’t have to change for him?’

‘Maybe.’ At last Perez did speak. ‘Or somewhere for Agnes to relax . . . ’

‘Would she have been able to climb the steps?’

‘Not at the end,’ he said. ‘But when they first moved here she wasn’t so ill. And she was a lively woman. Full of laughter. She was an art teacher. Taught me for a while at the Anderson High. My last year at school. She was very young then. Very bonny.’

‘And Henderson kept the room like a kind of shrine.’

‘I don’t know,’ Perez said. It was as if he found the question ridiculous. ‘It was just an idea I had. I could be wrong.’