‘Mr Beeley, I need to know. Where have they gone?' Sam rallied momentarily, as if the tone of her voice had pierced his lethargy. He moved a hand feebly, not quite completing the gesture. 'Out on the Baulk.’

The old man sagged again. He was clutching his ivory-headed stick as if his life depended on it, and his bony hands were tense and white at the knuckles where they gripped the Alsatian's head.

Fry thought of her first visit to the smallholding. 'He doesn't look like he's got strong wrists, but it's all in the technique,' Wilford Cutts had said. She had seen those same hands break the neck of a large bird with one twist. She thought of the three old men, and she thought of Harry Dickinson covering up for someone involved in the death of Laura Vernon. Did it have to be family? She looked again at Sam, seeing him afresh. He looked like a defeated man; a man who had been in pain for years and was in agony right now, suffering in front of her eyes. But was his pain entirely physical?

‘Can I have a look at your stick, Mr Beeley?’

‘My stick? I've had it a long time.'

‘May I?’

She held out her hand, and Sam hesitantly gave her the stick. It felt heavy and solid and was well-made, so that it balanced properly and swung easily in the hand. The handle shaped like the head of an Alsatian was worn smooth and shiny by Sam Beeley's hands. The back of the dog's head formed a hard, rounded ball of ivory, easily capable of crushing a skull if wielded with enough force. Or, of course, with the right technique.

She examined the handle closely. There were no traces she could see. But then it could have been cleaned. And in six days of use, any visible traces of blood or tissue could easily have been rubbed off on to the parchment-thin palms of its owner's hands. The forensics lab, though, would soon settle it one way or another.

‘I have to ask you to come with me to the station to answer some questions,' said Fry.

Sam nodded wearily. 'I'll need to use my stick.'

‘I'm afraid you'll have to manage without it for a while.'

‘I can't walk without my stick,' he insisted.

Sam was trembling even more than usual. He looked as though he needed an ambulance rather than a trip to the station. Fry hesitated, conscious of the mistakes that had dogged the enquiry so far. The last thing she needed was a sick old man suffering a collapse in police custody.

As her brain ticked over, she found herself looking past Sam into the doorway of the shed. The interior was pitch black, but her eye was attracted by a quiet movement in the darkness. There was something in there that was blacker than the surrounding shadows, something with eyes that turned to watch her as she brought her mobile phone from the Peugeot. She needed advice on this one. Someone else could make the decision on whether to pull an apparently helpless old man in for questioning.

She got through to the duty officer in the incident room again, giving details of her location and asking for the whereabouts of Tailby and Hitchens. But the officer had news. And what he had to tell her made her forget about Sam Beeley for now.

Fry asked a few questions and requested whatever back-up was available at this time of night. Then she ended the call and dialled again, this time trying Ben Cooper's number. She needed to tell him this bit of news.

It was something he had to know before he encountered Harry Dickinson again.

According to the duty officer, a second search had been ordered that afternoon in the area of scrubland at the back of the Vernons' garden, this time seeking evidence of Andrew Milner's presence in the vicinity. The search had spread, almost by accident, into the garden itself. And there, at the bottom of a well-trimmed privet hedge, Laura Vernon's second trainer had been found late in the afternoon.

The man in the incident room was eager to talk. It was a lonely job in the evening, and nobody ever took the trouble to discuss the enquiry with him.

‘It caused a bit of excitement round here, I can tell you,' he said with relish. 'It went straight to the lab, and they found two clear sets of prints on the trainer. I thought Mr Tailby was going to hit the roof. Especially as the garden had been searched once already. But that's the way it always goes, isn't it?’

Fry held her breath, staring blindly at Sam Beeley and the shed behind him.

She heard that a fingerprint officer had worked late in the evening to lift the prints off the second trainer and compare them to those on the matching half of the pair. On the first trainer, they had found only Laura's own prints — identified by taking fingerprints from the body — and those of Harry Dickinson, who had carried the trainer back to Dial Cottage. Now the new fingerprint report had come through, and it showed that the two sets of prints were identical. It meant that Harry Dickinson had handled both trainers. But only one of them had been found with the body. Who else could possibly have touched the other one, except Laura Vernon's killer? Ben Cooper's phone rang and rang unanswered. Fry knew, of course, that he had left his phone in his car. But still she let it ring. Echoing in her mind was that one sentence he had used that had trapped her into being here tonight, in this crazy situation. 'Are you going to let me down?' he had said.

While she waited, biting her lip, she found her eyes growing accustomed to the darkness in the doorway behind Sam. And now she could see, all too clearly, what was in the shed.

*

For a while, Ben Cooper was able to keep the two figures in sight from a safe vantage point among the rocks on Raven's Side. Gradually, he worked his way down the steep hillside, using the cover of the rocky outcrops and the first of the trees on the lower slopes. The two old men weren't moving quickly. They looked as though they were out for a Sunday stroll, ambling along the path close together, almost shoulder to shoulder, apparently deep in conversation.

Cooper was glad of their absorption in each other as he scrambled down a stretch of open ground, stumbling on invisible rabbit holes and stubbing his toe on half-buried stones. Before he had reached ground level, Harry and Wilford had vanished around a bend in the path. He remembered a second path which ran at a diagonal across the face of the cliff and emerged on to the main path heading towards the Baulk. He found it quickly and broke into a run, lifting his feet high off the ground and letting them fall as softly as he could, afraid of unseen hazards that might trip him, but desperate to gain distance on the two old men. The surrounding trees grew tall and dense, and a thick, muffled silence gradually descended around him, cutting him off from the world that had existed higher up on the tors.

As he ran, Cooper thought of Diane Fry's interview with Charlotte Vernon. If she really did visit the Baulk every night to contemplate the place of her daughter's death, then Harry Dickinson would surely know it. There seemed to be very little that went on in this area that Harry wasn't aware of. No doubt he had seen Charlotte picking her way along the path with her bunches of flowers, just as he had spotted her husband out on the Baulk. Cooper wondered what Harry's real intention had been when he set off to try to meet Graham Vernon the night that Laura had died. And he wondered whether Harry now meant to follow up that intention with Vernon's wife instead. There was no doubt in Cooper's mind that danger lurked in the woods tonight.

For once, Harry was without his dog, Jess. But he was accompanied by Wilford Cutts instead. Probably there was little to choose between them for loyalty.

Cooper reached the main path, breathing hard, and turned westwards towards the Baulk. Down below him now, on his right, was the stream and the Eden Valley Trail that ran alongside it. Faintly, through the covering of trees, he could hear the whispering of the water. Abarn owl called — an eerie, long-drawn-out hunting cry that echoed across the valley and was enough to make him shiver, even though he knew what it was.