Cooper listened. All he could hear was the wind which caught at him now they were on the plateau. It carried a whispering in the bracken and the jingle of the chimes. He listened more carefully. He heard several types of bird call – finches twittering nearby, a robin singing in the birches, the jackdaws in Top Quarry; and something else further away, possibly rooks and a blackbird. There was nothing more. Cooper looked up. There was a kestrel hovering over the rough grass on the edge of the quarry, but it was absolutely silent.

‘Do you hear it?’ said Stride. ‘That’s great.’

‘The edge of what?’

‘The reality zone. From here on, all that stuff down there disappears.’ He waved vaguely in the direction of Matlock and the A6.

‘Not for me, it doesn’t.’

Suddenly, Stride threw himself full-length into the damp bracken. For a moment, he disappeared completely as the brown leaves closed over him. Only his laugh could be heard from somewhere in the dripping depths.

‘Look at this!’ he said. His head appeared. He wiped a bracken leaf across his face, smearing the rain water on his skin and licking the moisture off his lips, closing his eyes in ecstasy. Bits of foliage and fragments of dead heather were clinging to his hair and shoulders; the sleeves of his jacket were soaked.

‘I suppose you think this is just a weed. Farmers tear it up and burn it, because it’s a pest. But bracken is a miracle. All ferns are a miracle. Look, look.’ He stroked a tiny, furled leaf. It would probably never open now – it was too late in the year. ‘Each of these produces hundreds of spores. They’re spread around by the wind or animals. I’m doing it now. Look!’ He rolled over on the ground, laughing breathlessly. ‘I’m part of the process! I’m part of nature!’

Stride plucked a larger leaf and held it in front of Cooper’s face. ‘Every spore that lands grows into a little disc. And do you know what? It has both male and female sexual organs. It’s a bisexual. Humans will tell you that isn’t natural. But it is!’

He thrust the leaf into Cooper’s hands. It smelled damp and green and broken. Cooper held it lightly, not sure what to do with it, reluctant just to walk away, too intrigued by the performance to stop it.

‘The male organs release sperm. Oh, yes. We know about sperm, don’t we? But ferns . . . their sperm use the rain water. See? The leaves are always damp up here, in the autumn, so the sperm can travel through the moisture to reach the female organs and fertilize the eggs. And then a new plant grows. A new fern. More bracken. More and more of it. And you know what else? Ferns have been doing that for three hundred million years.’