Perez eased himself out of the car. His joints already felt stiff from sitting still for so long. He walked along the road, missing the path occasionally and feeling the soft grass of the verge beneath his feet, because the darkness was almost liquid, so dense that it seemed to be drowning him.

He’d stopped for breath and in an attempt to get his bearings, when he heard footsteps on the road ahead of him. They were moving away from him and that was what he’d been expecting. It was past midnight now and this wasn’t the weather for an innocent night-time stroll. He stood very still and the sound of the footsteps disappeared into the distance.

He followed slowly, treading carefully to make as little noise as possible. This is ridiculous, he thought. We could be bairns playing hide-and-seek. This isn’t a professional way to carry on. Suddenly, there was a square of light that had come out of nowhere. It was like a beacon on the land above him. It must be an uncurtained front window in Jackie and Andrew’s grand house on the hill. He thought the fog must be lifting a little if he could see that from the road. Now he was sure where the murderer was heading and he felt less lost, with at least one landmark to give him his bearings. He imagined the men going out in the Shetland Bus on nights like this with no radar and no GPS, just a chart and a compass.

Approaching Setter he felt a breeze on his face and he thought again that the mist was clearing. He must be close to the croft now, but Sandy had done as he was told and there were no lights on. Perez wished he could talk to Sandy, to warn him they were on their way, but didn’t want to risk the noise of a conversation or of a phone ringing in the house. The murderer had killed twice before and was unpredictable. He stopped walking and there was total silence except for the regular and occasional moan of the foghorn. In the distance there was a tiny, moving spark: a torch being carried by the walker. It hadn’t been visible when the fog was most dense.