The group were standing on a path with trees behind them. The background was fairly unremarkable and undistinguished, except for one thing. The most striking detail in the picture was a London Underground train on a track in a dip between the group and the belt of trees. The last carriage of another train could just be made out past Sandra Blair’s head. It looked as if the train were drawn up in a sidings.

There was one more photo. It was of Sandra herself, standing on her own. The shot was taken by flash at night, so her skin was washed out and pale, her eyes flared red, her figure stood out in unnatural detail from her surroundings as if she were an illusion or phantom. In that instant of the flash going off, Sandra Blair already looked like a ghost.

‘What’s the date stamp on this?’ asked Cooper.

‘October thirty-first.’

‘The night she died.’

Cooper peered more closely. Though the colours weren’t accurate, he could see Sandra was wearing the same clothes that her body had been found in, including the blue waterproof jacket and the walking boots. And he’d been right about the hat. It was woollen, with ear flaps and decorated in some kind of Scandinavian design. Sandra’s dark hair peeped out of it over her forehead. She was holding something in her hand, close to her body. Cooper couldn’t see what it was, but his bet was on a torch. That was missing from the scene too.

‘Can we zoom in a bit?’ he said.

‘Sure.’

In the background he could make out the distinctive arched outline, only just visible but recognisable, even in the darkness. Its wet, moss-covered stones glittered eerily in the light of the flash. Sandra Blair was standing right in front of the Corpse Bridge, no more than a few feet from where she died.

Cooper asked Abbott to go back to the group shot again.

‘Yes, strange, isn’t it?’ said Abbott. ‘A couple of Tube trains. It must be in the London area somewhere. There are no Tube trains in Derbyshire.’

‘Where do you live, Wayne?’ asked Cooper.

‘Me? In Sheffield.’

‘That explains it.’

Abbott stared at him in puzzlement. But Cooper was remembering what Poppy Mellor had said. They walked all the old coffin roads. Of course they did. And this was one of them.

‘No Tube trains in Derbyshire?’ he said. ‘Actually, I think you’ll find there are. Or at least, there were when this photograph was taken.’

DC Luke Irvine had been sent to Bowden with Carol Villiers. They parked near the church and walked across to Jason Shaw’s address.

Villiers had seen Shaw before, but it was the first time Irvine had set eyes on him. He was recorded as being in his early thirties. Irvine noted the dark stubble. He envied the silver ear stud – he would have one himself, if he could.

They’d found Shaw in a small backyard behind his cottage. It was paved and only large enough to contain a couple of wheelie bins and a dog run. A blue Land Rover Discovery was drawn up by the side wall.

The dog began barking before they went round the corner of the house, so Shaw knew someone was coming. He’d put down a bowl of dog food and some water in the run and was just closing the door. The dog was a collie cross of some kind. Irvine couldn’t have been more accurate, though he was sure Ben Cooper would have known.

Shaw knew who they were straight away. He didn’t seem at all surprised.

‘I thought you lot would be here before long,’ he said.

They showed him their IDs anyway. The dog began barking again, but Shaw yelled at it and it cowered away from the fence.

‘You know why we’ve come, then,’ said Villiers. ‘You didn’t tell us the truth when you came in to make a statement in Edendale on Saturday morning.’

‘I didn’t lie,’ said Shaw. ‘I told you some of the truth. The part that mattered.’

‘Well, we don’t agree with that attitude, sir. It all matters to us.’

Shaw wiped his hands on his jeans. ‘I don’t see that it’s relevant. I came forward like a good citizen when I heard the appeals. That’s the end of it.’

‘Obviously we have to ask you about the protest group you’re a member of. We need to know what was going on last Thursday night at the bridge.’

‘I honestly don’t know what I can tell you about the group,’ said Shaw.

‘You didn’t tell us anything before.’

‘Okay, but – you’ve talked to some of the others already, haven’t you? So you’ll know all about it by now. More than I could tell you, anyway. I’m just a humble foot soldier. The others are the ones with the brains. They did all the talking and I just trailed along behind, if you get my meaning.’

‘So who sent the threatening letter to the Manbys and wrote graffiti on the wall of the chapel at Knowle Abbey?’

Shaw shrugged. ‘No idea,’ he said. ‘I don’t think that was ever part of the plan. Somebody taking a bit of individual action, by the sound of it. Graffiti? Ask Rob Beresford, that would be my suggestion. It sounds like his sort of trick.’

‘And what about Sandra Blair?’

He stalled for the first time and looked genuinely upset for a few moments. But the expression passed. ‘That was a real shame. She was okay, Sandra. I bet the others told you she was a nutcase. Well, she was a bit wacky in some ways, I suppose. But she meant well.’

‘You were with her that night at the bridge, weren’t you?’

‘Only up to a point,’ said Shaw.

‘What do you mean?’

‘Well, I had her stuff in my Land Rover – you know, the effigy thing and the other bits and pieces.’

‘A noose? A witch ball?’

‘I think that was it. I’d collected the stuff from her earlier in the week. Then that afternoon, when she finished work, she walked across from Crowdecote and I met her in Longnor, in front of the general stores. She wouldn’t have got her own car anywhere near the bridge, you see. But with the Land Rover, I got right down to the last few yards, until the track was too broken up. I mean, she wouldn’t have wanted to walk down to the bridge with those things. If anybody had seen her, that would definitely have looked weird.’

‘Then what did you do?’

‘I left her to it,’ said Shaw.

‘You left her there on her own?’

‘Yes. Well, she was on her own when I drove back up the track. I had to get the Land Rover clear. If anybody saw it going down, they would just think I was another off-roader. But if it was parked by the bridge for a couple of hours, well – that looks suspicious.’

‘Who worked all this out?’ asked Irvine.

Shaw laughed. ‘Not me, anyway. I just did what I was told.’

‘So why were you there on the track again later?’

‘Once I shifted the Land Rover, I was supposed to go back. That was the plan. We were going to get photos when it was all set up. The group standing round the noose. We’d have our faces covered by hoods and scarves. It was going to be like a terrorist video – you know, when they kidnap some tourist and put pictures on the internet standing round him with their Kalashnikovs. You know what I mean?’

‘Yes. But it didn’t happen, did it?’

‘No,’ said Shaw. ‘Well, I told you the rest, when I came in the first time. I don’t know any more than that.’

‘You’re saying you have no idea what happened to Sandra Blair at the bridge?’

‘Not a clue. Did … did someone do that to her? They killed her?’

‘Who do you think might have done that, Mr Shaw?’

‘I don’t know.’

‘One of the group?’

‘Like who?’

‘You tell me.’

He shook his head slowly. ‘I honestly can’t imagine. I mean, they didn’t always see eye to eye. They argued sometimes. Particularly…’

‘Yes?’

‘Well, Sally Naden. She didn’t think much of Sandra. I heard her say once that Sandra was a liability. But it wasn’t serious. She would never kill her. Why would she do that? It doesn’t make sense.’

‘It was your suggestion.’

‘I’m just trying to help.’

‘As it happens,’ said Villiers, ‘the post-mortem examination suggests that Mrs Blair wasn’t deliberately killed. She may just have had an accident.’