‘What happened after the sledge tipped over? How did Andy look?’

‘All right. He was laughing about it. And then …’

‘Then?’

‘He called to me that he’d found something in the snow.’

‘What had he found?’

‘I don’t know. It looked like a blue ball.’

Selby said: ‘You saw it?’

‘Only a glimpse of it. Then Andy fell over.’

‘I see.’

There was hardly likely to be a blue ball in the rubble brought down a desolate mountainside by an avalanche. A blue boulder, probably, sufficiently spherical to look like a ball. The only odd thing was that, if Stephen had seen it, so should he have done when he picked Andy’s body up. He had an exact recollection of the scene: the snow broken but homogeneous. No sign of blue in the white. No boulders.

‘You didn’t pick it up,’ he asked, ‘when you went to help Andy? Whatever it was.’

‘There was nothing there, then. But there was something before. Bright blue and – well, gleaming.’

Some kind of illusion, Selby decided. He knew that sunlight on snow could play odd tricks with the eyes.