While they were scrambling up towards the hole, Henry turned his headlamp, for the last time, on the cave which they were abandoning. The water level was very close to where they stood. Its steady, almost perceptible rise was frightening. Cynthia thought of what it would be like in a few hours, with the cave flooded to more than three times a man’s height, and the water still steadily pouring in, and out again through the hole in the wall.

She said: ‘It will follow us, won’t it? The water.’

‘It may not. We don’t know what the ground’s like on the other side. In any case, I hope we can get well above this level.’

She said softly: ‘I’ve been thinking – there’s one good thing.’

‘What?’

‘We none of us have children to leave.’

He took hold of her wrists; his touch was the touch of a stranger – harsh, meaningless.

He said: ‘You mustn’t talk like that, Sinner.’