Northwards from Monsal Head he passed opencast limestone workings and turned right towards Foolow and Eyam. After a call at a disused quarry that was used as an unofficial car park for walkers following the Limestone Way, Cooper found himself crossing Eyam Edge and arriving, as he knew he must, on the road into Moorhay.

He parked the Toyota at the Old Mill at Quith Holes, persuading himself that this meant he was still pursuing his routine enquiries into car crime at local tourist spots. There were plenty of other cars at the Old Mill, and several families were seated at the tables set out on the grass. A cluster of cottages were set behind the mill on a narrow road protected by 'private' no entry signs.

Cooper crossed a small stone bridge near the original ford and took the path that skirted Raven's Side, wincing at the bruises on his legs and back but glad of the opportunity to loosen up his limbs. He had to consult his OS map, because he hadn't approached the path from this direction before. But by following his instinct and steering slightly downhill, he soon reached the area where he had walked to with Harry Dickinson four days previously.

Once again, he left the path and crossed the tumble of boulders to the spot at the top of the slope above the stream. There was no sign of the crime scene now, except for a wide, bare patch where the undergrowth had been cut down to the ground and removed to the forensic laboratory.

He peered down on to the stream below. He knew there was nothing he could see that wouldn't already have been found and identified by the SOCOs. But sometimes he did get feelings that he couldn't account for. He didn't talk about these feelings much at E Division. He couldn't afford to be considered an eccentric. In the police service, you had to fit in; you had to be a team player and follow the rule book. Now, though, he was hoping that some feeling, some small insight, might just strike him at the place where the body of Laura Vernon had been found. Somewhere at the back of his thoughts, indistinct and deadened by the remains of his hangover, was an idea that had been suggested to him sometime last night. Something to do with dogs. Or was it pigs? Cooper found his mind filled with a vivid image. He saw a sharp, black muzzle filled with white teeth that snapped and tore at pale, dead flesh. Behind the fangs were jaws dripping with saliva and a pink tongue that curled and twisted and rolled out a rumbling growl from deep in a fur-covered throat. Fierce red eyes stared madly as the teeth bit and pierced. The white skin darkened and punctured, but there was no blood. He saw the dog finally letting go of its victim and looking up at the dark, contorted shapes of the Witches as it began to howl, its dirt-encrusted claws scrabbling in the earth with frustration. The black dog had come for a soul, and had been thwarted.

But that wasn't it. Cooper shook his head to clear the image. He knew the black dog was his own. He had carried it around in his mind since childhood, and it was him that it had come to claim, not Laura Vernon.

After several minutes, he was forced to give up and move on, with no great inspirations. He walked back to the path and looked up the hill. He ought to go back to Quith Holes now - back to the car and his routine enquiries. He was off the Vernon case.

But instead he turned and began to walk up the path towards Moorhay, his muscles protesting and the bruises on his ribs throbbing. Out of the trees, the sun beat on his back and neck, and he began to feel a bit light-headed. This was no way to restore himself as a candidate for a sergeant's job. But something had happened out here on the Baulk. Who had Laura Vernon met here? Had she met him by design or accident? Had she been followed, or had she walked down this path with someone she had spoken to behind the garden at the Mount? The final results of forensic tests might reveal some of that information. So far they had at least established that the bite mark on the victim's thigh had been the work of canine teeth. A dog, possibly. But it could just as easily have been a fox, coming across the dead body as it lay in the undergrowth attracting maggots. But would forensics reveal the identity of the killer? Cooper didn't think so.

When he got to within a hundred yards of Dial Cottage, he almost bumped into Harry Dickinson, who was standing under a tree in the shade, with his dog at his feet. He stared wordlessly at Cooper, like a man interrupted in his own sitting room.

‘Oh, you.’

Aye, me. Like a bad penny.'

‘Not your usual time for walking the dog, is it, Mr Dickinson?'

‘I needed to get the taste of your police station out of my mouth, lad.'

‘So where have you been?'

‘Minding my own business.’

Cooper was hot and sore, and felt himself starting to get angry. But Harry only tilted his head, revealing his unfathomable eyes.

Are you going to arrest me again? There are no young lasses in these woods, you know — not at this time of day.'

‘I don't think it's a subject to joke about, Mr Dickinson. Do you?’

Aye, maybe you're right, lad. Maybe I've had enough enjoyment for one day.’

The hint of bitterness in the old man's voice made Cooper's ears prick up. Evidence of emotion was rare enough from Harry. There was an air of finality in his words too, a feeling of something coming towards an end. He'd had enough — but enough of what?

‘They had Jess in a cage at that police station,' said Harry. 'Shut up in a cage with a lot of mongrels and strays. What has she ever done wrong to anybody? Tell me that.’

Cooper felt a strange sensation coming over him, a powerful physical surge that sent a shiver of excitement up his spine. His eyes were drawn down to the ground, where Jess, the black Labrador, was lying on the grass at Harry's feet. Her lolling pink tongue was the only splash of colour in a tangle of black fur.

‘Right,' he said, catching his breath. 'Yes, that's right.' Harry looked at him sharply, suddenly suspicious at the silence. Cooper shook himself and stared back at the old man, beginning to smile for the first time in days.

*

Gwen Dickinson saw Ben Cooper coming up the path. She had been watching for Harry from the kitchen window. Her face was drawn, and her eyes were red from lack of sleep and too many tears.

Cooper remembered that she, too, had been questioned in an interview room at Edendale, to be informed that her husband was a suspected rapist. Suddenly, he felt sick at the thought of what was done to people like Gwen — innocent people who happened merely to find themselves on the sidelines of a major enquiry as unwilling witnesses, possessors of some snippet of information the police were determined to get hold of, while the foundations of their lives were being pulled apart in front of their eyes. For Gwen, he knew, life with Harry would never be the same.

‘What did he say?' asked Gwen, when he reached the back door of the cottage. She clutched at his sleeve as if expecting him to put everything right. 'I saw you speak to Harry.'

‘He didn't say anything. I'm sorry.’

Cooper didn't know what he was apologizing for. But he knew he had disappointed Gwen by the way her face fell and she turned to go back inside, shuffling her feet in a pair of old slippers decorated with pink roses.

‘Come in. Helen's here.'

‘Oh no, it's all right. I don't want to intrude.’

He began to back away, out into the sunlight. But Helen herself appeared in the kitchen at the sound of his voice. She was wearing jeans and a T-shirt and had a polishing cloth in her hand. Her red hair was tied back in a ribbon.

‘Come in, Ben. Don't stay out there, please.'

‘Helen's been doing a bit of cleaning for me,' said Gwen. 'I can't seem to be bothered with it any more.' As the old woman shuffled through into the sitting room and settled herself with a sigh into an armchair, Helen turned troubled eyes on Cooper.