The kitchen door, which had been open all day, so Perez had managed to catch reassuring glimpses of the women inside, was shut now. When he opened it, the room was empty. There was a big pan of water on the hob, the heat turned off. The smell of cooking: something sweet and appetizing. A pan containing thick custard, with a skin on the top. A big colander half full with chopped cabbage. Everything ordinary. Yet again Perez had the sense of a nightmare continuing. Sometimes, he thought, terror can be in the everyday. He shouted back to Sandy: ‘Who exactly did you see upstairs?’

‘Dougie and Ben. Ben was covered in blood and Dougie was helping him to clean up.’

‘What about the others?’

‘I thought they went upstairs. But maybe they came through the kitchen.’

‘Someone went outside,’ Perez said. ‘I heard the door.’

By now Sandy had picked up his boss’s panic. He looked close to tears and was perfectly aware of his own stupidity, his ability to cause the biggest cock-up in the world. ‘I’m sorry. I was in the dormitory. I didn’t see.’

In the enclosed space of the yard, Perez was hit by the cold. There was a faint gleam from a moon half-covered by cloud, and the bright occasional spot of the lighthouse beam. He ran through the gap in the whitewashed wall, ducking the clothes lines on the way, and looked out on the open hill. A thicker cloud covered the moon and suddenly it was pitch black. The sort of darkness you never get in a city. Then the cloud thinned again and he made out the silver line of reflected light that was Golden Water.

A woman screamed. Not Fran. He’d have recognized her voice, even as a scream. Thank God, not Fran. He raced towards the sound, tripping over the heather and outcrops of rock, splashing through the bog towards the loch. He was surprised by a movement at his feet, a slow beat of wings, saw a pair of eyes, yellow in the pale moonlight. A short-eared owl flying low over the hill.

The lighthouse lens circled and there was a brief snapshot before the beam moved on. The pool, a pale backdrop. Very black against it, a man’s silhouette, his arm raised. Perez saw the glint of light on metal, like a silent flash of lightning on a stormy night, before everything was dark again.