It was interesting to speculate, but Cooper wasn’t sure how it fitted in with the inquiry. The mine shafts had been searched after the disappearance of David and Trisha Pearson, and there was nothing to suggest that Aidan Merritt had even had any contact with the Pearsons, let alone a reason to kill them.

So what else was there? Cooper tapped a pencil against his teeth as he gazed out of the window at the rooftops of Edendale. There was something that still eluded him, a memory that he hadn’t quite grasped at the time, and that was proving even more elusive now. He hoped it would come back to him at some point when he wasn’t thinking about it.

DI Hitchens stuck his head round the door.

‘Ben, have you got a minute?’ he said.

Cooper went into the DI’s office. Hitchens looked weary, drained of energy. He had a leaflet on his desk promoting a seminar for inspectors. Meeting the challenges of the new performance landscape.

‘I wanted you to be the first to know, Ben,’ he said. ‘I’ll be moving on soon.’

‘Really?’

‘Yes, one way or another.’

Cooper sat down. He didn’t quite know how he felt about that. He was used to his DI, who had served in E Division for years. But everyone moved on eventually – especially if they were the least bit ambitious and wanted promotion. It always created a bit of uncertainty, though. Who would they get in his place? Hitchens might not have been the most dynamic DI, particularly in recent years. But sometimes it was better the devil you knew than the devil you didn’t.

Automatically, Cooper’s mind began to run through potential candidates for the job, those in other divisions rumoured to be tipped for promotion or transfer. On the other hand, might the DI’s departure create a vacancy that would be filled internally?

‘And you’ll be losing DC Murfin soon,’ said Hitchens. ‘How do you feel about that?’

‘Gavin has a lot of experience,’ said Cooper, immediately conscious that he’d said it before, and not just once. Was it starting to sound as if he was damning Murfin with faint praise?

‘Experience, yes. It’s worth a lot. Or it used to be, anyway. Everything is different these days, as you know. We have to make cutbacks everywhere we can.’

‘We’re not likely to lose anyone else, are we?’ said Cooper.

Hitchens shrugged. ‘Who can say?’

Murfin himself looked surprisingly chipper this morning. His desk in the CID room was cleared of forms and was now uncharacteristically tidy.

‘Diane Fry won’t be here much longer, I suppose,’ he said. ‘She’ll have her inquiry tied up in no time, and she’ll be off back to EMSOU – MC.’

‘Yes, I wouldn’t be surprised,’ said Cooper. ‘Why, were you thinking of inviting her to your retirement party?’

‘Maybe. It’s been interesting.’

‘Interesting? In the Chinese sense?’

Murfin gazed out of the window with a smile. ‘Well, we might all have learned something from the visit,’ he said.

Cooper followed his gaze. He could see Diane Fry’s black Audi in the car park at the back of the building. She’d reversed it into a spot near the extension where the scenes-of-crime department was now located.

‘What’s that on her rear bumper?’ said Cooper, his face crumpling into a puzzled frown.

‘I can’t imagine,’ said Murfin.

‘But it looks like …’

‘Oh,’ said Murfin overtheatrically. ‘So it does.’

‘Gavin?’

‘Yes, Ben?’

‘I suppose I shouldn’t ask.’

‘No, that’s probably for the best.’

‘It’s going to be another mystery, then,’ said Cooper.

‘You mean, how …?’

‘Yes. How Detective Sergeant Diane Fry, of the East Midlands Special Operations Unit – Major Crime, came to have an inflatable sheep tied to her rear bumper when she left West Street. And it seems to be wearing lipstick and eye make-up, too.’

‘I suppose it’s just a memento,’ said Murfin. ‘One last sheep to remember us by.’

Early that morning, a retired firefighter from Glossop called Roger Kitson arrived at Brecks Farm, near Peak Forest, along with hundreds of other people. He followed the directions of a steward as he drove his car through a gateway and into a field where vehicles were already lined up, many of them muddy Land Rovers and other four-wheel drives.

Roger was there for one of the biggest events of the year in the stretch of country around Oxlow Moor – the annual sheepdog trials. Every year, the trials were held in fields behind Brecks Farm, going on all day from seven thirty in the morning to around six in the evening. As well as the feats of the sheepdogs themselves, there was a children’s play area, side stalls, and plenty of food and drink to make the day.

But one of the real highlights of the event was a four-and-a-half-mile fell race, and that was why Roger Kitson was at Brecks Farm.

Roger was sixty-two years old, but he was a runner – a member of a club based near Stockport. Fell running was a gruelling sport, but it was more about stamina than strength. Last year, a couple of members from Dark Peak Fell Runners had finished the Oxlow Moor course in less than thirty minutes, with the advantage of good conditions. They would face competition this year, though, as Roger saw there were teams entered from the Goyt Valley Striders, the Hallamshire Harriers and even the Hathersage Fat Boys.

Before the start of the race, he strolled round the field to see what was going on. He could tell that the trials had already begun, from the distinctive whistles and shouts of the shepherd piercing the morning air. A collie would be hard at work already, chivvying a reluctant bunch of sheep into a pen.

On a table near the secretary’s tent stood the gleaming NatWest Trophy, ready to be presented to the owner of the winning sheepdog, along with smaller trophies for Best Driving Dog and Best Young Handler. One local farmer was raising money for the Border Collie Trust by growing half a beard, and he was attracting a lot of interest from photographers.

Roger joined a mass of runners in shorts and colourful vests waiting to set off on the opening climb, all with their identifying bib numbers tied to their singlets. He recognised the DPFR in their brown vests with yellow and purple hoops, and knew he would probably be a long way behind them. As a spectator, he’d seen the leading runners coming in one by one, each checking a watch as they approached the finishing line. He didn’t mind what time he clocked up, as long as he completed the course. There was a trophy for the first veteran to finish, but he didn’t expect to come close to that.

Today, the runners seemed to be all ages, shapes and sizes, but Roger kept reminding himself that stamina was the key to fell running. He overheard runners discussing the relative merits of their Walshes, the performance of a pair of Racers against Elite Extremes. He was wearing Walsh running shoes himself – they were hard-wearing enough to cope with both rocks and the wet peat they would be running over when they were up on the moor.

And then the race got under way. Within minutes of the start, the back markers were already struggling on the steep, rocky ascent, and Roger was among them. He made slow progress in the first few hundred yards, manoeuvring for the best route over the uneven rocky ground, sometimes being obliged to use his hands to keep his balance.

Slowly he approached the top of the ascent. Up ahead, something seemed to be happening. The leading runners were on the moor and pounding over the heather. But just before the first descent, there was chaos, with runners milling around aimlessly as if they’d lost sight of the route.

‘What’s going on?’ Roger asked the runner in front of him.

‘I don’t know,’ he gasped.

They kept going, losing sight of the lead runners. As they crested the hill, Roger could see smoke in the distance, drifting towards the runners, a clump of dry heather bursting into flame.