Looking up the hill at the fire burning along the skyline, Cooper could see a helicopter hovering low over the moor, carrying a huge orange bucket full of water. It released its load to help douse the fire, and a moment later was heading back eastwards until it disappeared.

He glimpsed a farmstead sheltered by a belt of trees, reminding him too much of Bridge End. He imagined the farm where he’d grown up being threatened by a moorland fire. It didn’t bear thinking about.

And this wasn’t the first fire on Kinder. When he was younger, he’d walked across this moor while the peat below him was burning, warming the surface but not quite breaking through. It was a strange experience, like crossing a hotplate with clouds of richly scented smoke rising all around him.

‘How did it happen?’ he asked. ‘Isn’t the Fire Severity Index at its highest level already? The access land should be closed to the public.’

The ranger shrugged. ‘We can close access land all right, but we don’t have the power to shut public footpaths. Which is a nonsense, when you think about it – because a lot of those paths run right across access land anyway. People think they can hold barbecues in the middle of a tinder-dry moorland, as if they were in their back garden. Why don’t they all go home and set fire to their own property?’

Cooper spotted the fire service’s Argo making its way across the edge of the plateau, its fogging unit spraying water on to the advancing fire front. He remembered the whole of that part of Kinder being a bog at one time. You wouldn’t have been able to walk across it, even in summer, without your boots sinking into water and evil-smelling mud soaking through your socks. He could still hear the squelch of his footsteps, and smell the fetid gas that was released from the sodden ground.

But he knew there would be no bog up there now. That stretch of moor had been dry for years.

‘Which direction is it moving?’

‘Westwards at the moment,’ said the ranger. ‘Towards Hayfield.’

‘It won’t get that far, surely?’

‘No, we’ll have it under control before then. But we’re pretty overstretched. We’re having to pull in all the resources we can. The trouble is, some of the other fires aren’t completely damped down. They could flare up again.’

‘Like Oxlow Moor?’

‘Yes. Though there isn’t much left to burn up there, to be honest.’

High above him, bright red embers were floating like fireflies against the bank of black smoke, and Cooper could see for himself that the fire was heading westwards.

Just away to the west was Kinder Downfall, a cascade of water falling vertically among shattered rocks. It was the highest waterfall in the county, where the River Kinder hit the edge of the plateau. On blustery days, the water seemed to flow upwards as the wind caught it in mid-air and hurled it back over the edge.

Below the downfall, the dark waters of Mermaid’s Pool were reputed to be haunted by a spirit who could either grant eternal life or pull you under the surface and drown you. Myth said it was a site of ancient human sacrifices. He remembered looking down at the pool from the rocks and realising how obvious it was that it used to be much larger. You could make out the original shape from the slope of the ground, and from the beds of reeds standing where the shallower parts of the pool had been. It must have covered three or four times the area it did now, but its edges had retreated, the body of water shrunk to little more than a pond. It would be very difficult now to imagine anything living in there except a few small fish and the odd frog, let alone a water demon. Luckily the people of Hayfield didn’t go in for human sacrifices as much as they used to.

He became aware that the ranger had finished conducting an agitated conversation on his radio and was cursing.

‘What’s the problem?’ asked Cooper.

‘Our temporary reservoir on the moor has been sabotaged.’

Cooper knew what he meant. He’d seen the big orange tank sitting in the middle of the moors. Because of the risk of fire, every year the national park rangers sited one of the water tanks out on Kinder. They held more than fifty thousand litres of water, and were large enough for a helicopter to lower its dipper bucket into, if necessary. Due to the remote nature of the moorland sites, tanks were often vital to prevent a fire from spreading. They usually stayed up there throughout the summer, and could be refilled from bowsers towed by rangers’ Land Rovers.

‘We had reports that the tank was empty, and when it was checked we found that somebody had cut the side of it with a knife,’ said the ranger. ‘The original cut was only about eighteen inches long, but the force of fifty-four thousand litres of water ripped a ten-foot hole. That’s impossible to repair. We’re just left with a big collapsed balloon.’

‘What does that mean for Kinder?’

The ranger followed Cooper’s gaze up the hill.

‘The consequences of losing that tank could be devastating. They helicopter is using Ladybower Reservoir instead, but it takes a lot longer. We were hoping to stop the fire in its tracks, but that won’t happen now.’

‘A few more square miles destroyed, then.’

‘You can bet on it.’

‘And it’s Kinder, too.’

‘Yes, Kinder. What can I say?’

Kinder Scout had its own unique history. Britain’s national park movement had started right here in the 1930s, when four hundred ramblers from Manchester staged a mass trespass on to grouse moors owned by the Duke of Devonshire.

The 1932 Kinder Trespass was the turning point in the campaign to open up access to the countryside. Five young ramblers had been jailed, and the resulting waves of support had ensured that Kinder was included when the first national park was created in the Peak District after the Second World War. Eventually, a later Duke of Devonshire had apologised for his ancestor’s actions. How times changed.

It was an episode recorded in Derbyshire Constabulary history, too. About a third of the force had been deployed around Hayfield to intercept ramblers taking part in the trespass. One hiker convicted of assault on a gamekeeper had protested his innocence right into his eighties. It had taken an enlightened chief constable to make amends for that one.

Cooper went back to his Toyota. He had to accept that there wasn’t much he could do, short of grabbing a beater and going up on the moor himself. Being here was just tormenting him, and he might even be getting in the way. He wished the ranger luck, and left.

Near Upper Booth, a couple of cars had been turning in a field entrance, and came slowly past him down the road. A silver Mercedes and a pale blue VW. As they passed, Cooper saw that their paintwork was covered in black specks, a shower of oily soot from the moorland fires they’d been watching with such enjoyment.

It looked as though the ranger’s prayers had been answered. The wind had changed direction after all.

At West Street, Cooper sat down at his desk and tried to get his thoughts in order. It was taking a bit of an effort this morning.

He remembered first of all that he’d arranged to meet Josh Lane at the Light House later on. The cellars were one part of the pub he felt sure hadn’t been looked at. Since nothing seemed to have been taken, a reason for the presence at the Light House of either Aidan Merritt or his killer still hadn’t been established. But what might be in the cellars?

He was picturing a motorcycle now. That was Roddy who’d put the idea into his head. But Maurice Wharton hadn’t been the type to ride a motorbike – or any of his family, except perhaps his son. Eliot was old enough to have a driving licence at seventeen, but he would have been too young when they lived at the pub.

Ah yes, Aidan Merritt – that was the second thing. According to Mrs Wheatcroft, Merritt’s father had been interested in the abandoned mines, and knew the locations of all the old shafts, maybe some that had been lost for a while. Had Aidan picked up some of that knowledge from his father?