Villiers got out to direct him back to the gateway. By the time Cooper had turned the Toyota round, a Traffic car was coming up the road towards them. The officer driving lowered his window when he recognised Cooper.

‘Yes, it’s bad,’ he said. ‘But the wind is shifting so much we can’t keep track of which routes are being affected. I keep expecting to come across an RTC, but so far we’ve been lucky.’

Cooper could see the likelihood of a road accident in these conditions. It only needed one unsuspecting motorist to come round a corner too fast. It happened often enough anyway, without the additional hazard of reduced visibility.

‘We’ll leave you to it then,’ he said. ‘Good luck.’

‘Oh, thanks.’

When he and Villiers got to the higher ground on the main road, Cooper had a clear view across the valley to the burning moorland. Only then did he realise that the ribbons of smoke they’d run into stretched for miles. Black clouds rose against the sky on the high plateau, swirling and breaking to reveal banks of flame scattered across the moor. Within a few yards of the fire the smoke dipped suddenly where it was caught by the wind. From there it slithered down the hillside, forming long trails like black fingers reaching towards the houses in the valley below.

‘We’re going to run into that smoke again in a minute,’ said Villiers.

‘You’re right.’

‘And it’s even worse there, Ben. It’s thicker and blacker.’

‘We can’t avoid it,’ said Cooper. ‘It’s directly above the road.’

‘Take it steady, then.’

‘Of course. You know me. I always do.’

They began to descend the steep hill towards the town of Edendale. And a few moments later, the sun went out.

By the time his hands touched the wooden boards, Aidan Merritt was nearly blinded by the tears streaming from his eyes. He banged on the boards with his fists, fumbled along the edges of the wall where the door frame should have been, but found no crack to get a grip on.

Desperately, he felt further along the stone facade. There had been windows here at one time, but they too had been boarded over. He tugged at a corner of a board, but couldn’t shift it. He realised the building itself had been blinded. No door, and no windows. It was an eyeless dinosaur abandoned in the burning landscape.

Finally he found a side door left open a crack, and slid inside. It was so good to be out of the smoke. But the interior was even darker – pitch black as a cave, thanks to the boarded-up windows. No doubt the electricity was off too. He could smell the mustiness that always invaded empty buildings, though the pub hadn’t been closed for all that long. Decades of stale beer and cigarette smoke were coming into their own now, oozing from the corners and seeping out of the floorboards.

And there was something else too, lurking beneath the mustiness. A thick, rank smell that seemed to stick to the mucus in his nose and throat. On top of the smoke, it made him feel nauseous. He struggled to control the instinct to gag. It was a stink like the smell of fear.

‘Hello!’ he called. ‘Anyone here?’

The sound of his own voice echoed back to him. He wasn’t certain what part of the building he was in. He had never used this side door when the pub was open. He might be somewhere near the kitchens, he couldn’t be sure. He would have to wait a few minutes for his eyesight to adjust to the darkness.

Merritt took a step forward, hands outstretched to feel for the presence of a wall or doorway. His boots crunched on broken glass. The noise sounded unnaturally loud, as if the glass had been left there deliberately as a warning of intruders.

‘Hello? Hello?’

There was no answer. Or was there? Did he detect a faint rustle in the darkness, the sound of breathing that wasn’t his own?

He turned quickly, overwhelmed by a sudden fear that there was someone behind him in the blackness. The broken glass squealed under his boots like a small creature crushed to death against the concrete.

‘Is that …? Is …?’

But the blow on his skull came out of nowhere. Merritt cried out in pain, saw flashes of blinding light in the darkness, felt his legs begin to crumple. Then a second impact drove consciousness from his brain, and he hit the floor, stunned and bleeding, with fragments of glass pressing into his skin, his eyelids twitching as his nerve endings spasmed in agony.

As he lay face down in the dust, Aidan Merritt never felt the third blow – even though it was the one that killed him.

2

The E Division headquarters building in Edendale was starting to look a bit grubby these days – in some parts as grimy as if it had been in the middle of a fire itself. Outside, the woodwork hadn’t been painted for a while, and the stone facing was becoming dark and mottled. Even the brackets for the lights near the security cameras looked as though they were being slowly eaten by acid rain.

As Cooper drove up West Street towards the police station, it seemed that only the rails to the disabled ramp stood out, bright yellow and gleaming in the sun.

But no, he was wrong. There was one other patch of yellow noticeable on the front of the building – the public phone used to contact officers at times when the station was closed. And the times it was closed were becoming increasingly frequent.

When they’d gone through the security barrier and parked among the marked vehicles and CID cars at the back of the building, Cooper locked the Toyota and stood for a moment looking up at the hills above the town.

Edendale sat in a kind of shallow bowl. In every direction you looked, you saw hills. Any road you took out of town went uphill. In the streets down by the river, the climate could be totally different from what was happening up there on the moors of the Dark Peak. A bit of drizzle falling on shoppers on Clappergate could have turned into a snowstorm by the time you reached the Snake Pass on your way to Glossop.

Today, though the sun was shining on Edendale, Cooper could see that the moors to the north and west of the town were black with smoke. It had been another dry spring, with little rain falling on Derbyshire for months. Despite heavy falls of snow in the winter, the high expanses of peat moor soon dried out. And it didn’t even need to be warm – this spring certainly hadn’t been. The plateaux were constantly scoured by wind, which evaporated the moisture and left the peat and banks of heather parched and vulnerable to the threat of wildfires. One January a fire had ignited at minus five degrees Celsius, burning dry winter vegetation above soil that was still frozen solid.

Summer could be a bad time too, when the sun was hot and more visitors crowded on to the moors. But at least there was new growth of foliage then. In the spring, there was only the old vegetation, woody and desiccated. Firefighters called it the fuel load. This spring, the moors were like a vast tinderbox, just waiting for a spark to create these catastrophic fires.

With so much flammable material, and ideal conditions, the fires could burn for days, or for weeks. To the north, near Sheffield, a moorland fire had been smouldering continuously since 1978, after it burned down through the peat into underlying strata of coal. Once that happened, there was no way to put it out.

‘I remember fires like these when I was growing up,’ said Villiers, coming to stand at his shoulder. ‘I thought the whole world was coming to an end. It was like Armageddon. I can’t recall what year it was, but I was quite young.’

‘The worst year was 1976,’ said Cooper.

‘What? I’m not that old.’

‘Nineteen eighty, then. And 1995, 2003 – they were all bad years. All showed spikes in the number of moorland fires.’