‘It’s possible. Even the automatic lights are kept immaculate. The guys who come to check the working wouldn’t have left that here. The search team haven’t found the pillowcase yet and I asked them to look. I’ll get them up here to check the place out. Don’t touch more than you have to now. There might be fingerprints.’

Fran expected Perez to climb immediately down the stairs to fetch Sandy and the other officers but he didn’t move. ‘I think the murderer has been up here spying,’ he said. ‘I wondered how he tracked down Jane to the Pund. From here you can see everyone’s movements at least in the north half of the island. He knows exactly what we’re all doing and where we are.’

She reached out and took his hand.

As they walked south again, the late afternoon sun was almost warm. Almost. They were still holding hands, like seven-year-olds pretending to be grown up, exchanging a few words. All about themselves, how lucky they were to have found each other, plans for the future. Sentimental stuff that had nothing to do with the investigation. Fran had assumed Perez would want to stay in the tower to supervise the search, but he’d decided to leave them to it. Fran was grateful for that, and for the knowledge that the murderer could no longer be up there, looking down at them. She felt ill whenever she thought that their intimate moments together could have been observed.

Perez’s phone hadn’t rung all day. Too good to be true, Fran thought suddenly.

‘Is your mobile actually switched on?’ His phone was a standing joke. An alternative form of contraception, she said. Always ringing at the most awkward time.

‘Shit! I turned it off for the kirk and forgot to switch it back on.’ He pulled a face, pressed a button. ‘Five missed calls.’ And the romantic walk through the warm autumn light was over. He was a cop all over again.

‘So tell me . . .’ His phone pressed against his ear with his left hand, scrabbling for a pen and paper with the other. They’d stopped and he leaned the paper on a piece of dry-stone wall. She squatted on a flat rock, looked back towards Sheep Craig, remembering the perspective of it from the tower, thinking again about the painting she’d make. His words were like background music in a bar. She heard them but didn’t take in the meaning. Perez scribbled on the paper, filled one side with his crabby, repressed writing and turned it over. His questions weren’t much more than promptings to persuade the caller to continue talking.

‘How long? So she would have known?’