Just before they vanished, the Virgins had seemed to move. They had shuffled right and left, faded in and out of focus, come closer and backed away, as if they had been caught for a moment in a celebratory dance. Then they had disappeared with a click and the whirr of a motor, flicking out of sight in a white glare, with tendrils of smoke left drifting in the beam.

Cooper shifted uneasily, frustrated by the inactivity. It was early in the morning, but his mind was already alert. In fact, his imagination was streaming ahead of the facts, and vivid images were flipping through his brain. Yesterday, he had stood on Ringham Moor himself. He had felt the bite of the wind up there, and listened to it hissing through the dying heather as the birch leaves crackled under his feet. And he had seen where all this started – with the stones.

One indistinct shape stood out from the others in the darkness. From the corner of his eye, a subtle change in the pattern of the shadows suggested a face had turned towards him for a second. Cooper felt the brief glance like a draught of air entering the room and stroking its fingers across his face. Suddenly, he felt self-conscious and conspicuous, afraid to move a muscle for fear of drawing attention to himself. He knew it was not in his interest to attract her attention. He wouldn’t know what on earth to say to her if he did.

A voice came out of the darkness. ‘Forty feet across, on a shallow, sandy floor. Drag marks nearly twenty feet into the centre. No signs of a struggle. However . . .’

The next slide appeared on the screen, bizarre and meaningless until the projector pulled it into focus. To Cooper, it looked as if an aerial shot had been taken from high above the earth, where the hull of an ancient boat lay half-buried in a desert. There was a ragged elliptical shape, dark red and scattered with black flecks. It was set in a strange, grainy yellow landscape like deep sand that blurred the edges of the shape and rolled away towards distant orange hills that cast no shadows.

He might have been looking at some kind of Noah’s Ark, stranded on a remote mountainside in Syria, the subject of endless arguments about its reality. The jagged black marks in the centre could have been the remains of a petrified wheelhouse, crumbled masts and decking, or rigging long since turned to dust. But there was no natural sunlight in this desert, only artificial colours.

Then a shadow moved in front of the screen, and a weary face was caught by the light of the projector.

‘You can all see what this is. It needs no explanation from me. Death would have occurred within minutes.’