Fry wasn’t amused. ‘I assure you, sir, I don’t hassle members of the public.’

‘Of course not, Diane. You’re a model of respect and discretion.’

She felt her jaw tighten, and tried to relax her muscles in case she looked too tense or aggressive.

‘But it’s hardly surprising the family feel that way, is it?’ said Hitchens. ‘Let’s not forget that they’ve lost both their children and two of their grandchildren in the course of a week. And now you want to hunt down their son-in-law and their remaining grandchild.’

‘It’s not like that at all.’

‘But that’s the way it’s going to seem to the Lowthers. Let me tell you, I never want to experience as uncomfortable a half hour as I spent with those two people this morning.’

‘I’m certain Brian Mullen is going to turn up at the Matlock Bath illuminations tonight,’ said Fry. ‘As certain as I can be.’

‘Your grounds for that belief seem to be very tenuous, to say the least. Why would he risk taking the child to Matlock Bath?’

‘It was something he’d promised the family. Even with only Luanne left, I think he’ll follow through on the promise. Especially with only Luanne left.’

‘I see.’

‘There’s more. I’m concerned that this visit could be the prelude to a significant act on his part. I think Mr Mullen is planning to do something rash and desperate.’

‘What do you mean?’

‘My feeling is that, unless we find him tonight, it could be too late.’

The DI swivelled his chair again, making Fry grind her teeth with frustration.

‘It’s not like you to base your reactions entirely on gut instinct, Diane. Have you got a personal problem with this case?’

‘No, sir.’

Hitchens watched her, waiting to hear more, perhaps hoping she could give him some solid justification. But Fry had already exhausted what she had to say, and stayed silent.

The DI looked disappointed. ‘Well, I’m sorry, but I can’t authorize an operation to apprehend Mr Mullen at this event in Matlock Bath tonight. I’ve heard nothing to justify the use of resources for such a wild-goose chase. Let alone the effect on the family, which you don’t seem to be taking into consideration. You could land us with an even bigger public relations disaster than we already have.’

Fry stood up to leave. ‘Thank you, sir.’

Hitchens held up a hand to keep her back. ‘You haven’t asked me about Tony Donnelly.’

‘Is there any point?’

‘I re-interviewed him this morning.’

‘How many “no comments” did you get?’

‘A few,’ admitted Hitchens. ‘We’re going to have to put some effort in on Donnelly, interviewing his family, friends, neighbours. His background will have to be looked at, his whereabouts checked, alibis pursued …’

This time, nothing would keep Fry from leaving the DI’s office.

‘Are you sure there’s nothing else you want to talk about, Diane?’ he said.

‘Yes, thank you. Quite sure.’

Cooper saw that he’d been right. There were so many visitors trying to get into Matlock Bath that by five o’clock all the car parks in the village were full. Police officers in yellow jackets were directing long queues of motorists to a park-and-ride facility at the rugby club a mile down the road. The pavements were packed with people queuing at the fish-and-chip shops or eating out of paper packages as they leaned over the railings to gaze at the river, throwing their last few chips to the ducks. Many of the crowd were family groups, young children sitting in pushchairs or strapped to the parents in carriers.

It had already been gloomy enough by half past four to use sidelights as they drove down from Edendale. On the way here, the mood had been sombre. Dead leaves had filled the lay-bys like a yellow tide.

‘I have to remind you that we’re here unofficially,’ said Fry. ‘Strictly speaking, you’re off duty.’

Cooper nodded. ‘We understand that, Diane.’

‘No overtime, then?’ said Murfin.

‘No overtime, Gavin. Sorry.’

Murfin shrugged. ‘It gets me out of the house. And it means you can’t tell me not to eat fish and chips while I’m working, right?’

‘Right.’ Fry looked at Kotsev. ‘Georgi? There’s no obligation on you to be here at all.’

‘What else would I be doing? Sitting in my hotel watching English television? I wish to be part of the team.’

‘Thanks, Georgi.’

‘And I’m not to beat up any suspects, OK?’

Fry glanced at him, seemed to recognize that he was joking, and let it pass.

‘I’ve told the inspector in charge of the uniformed operation that we’re here, but I didn’t give him any more details than he needs to know. He’s far too busy to bother about us, anyway. He’s expecting a crowd of six thousand people and a lot of traffic problems. All he’s got to handle it are a dozen bobbies and a few CSOs.’

‘So what are we looking for exactly?’ said Murfin.

‘Brian Mullen. And, I hope, Luanne.’

Cooper coughed uneasily. ‘Diane, if your theory about Brian Mullen is right, what will happen to the child? Will she be sent back to Bulgaria? Surely she wouldn’t have to go back to her real father after all?’

But Fry’s face was hard, giving nothing away. ‘That won’t be our decision to make. All we have to do is find them.’

‘So our responsibility stops there, does it?’

‘Ben, I hope you’re not going all social worker on me again.’

‘But don’t you sometimes wonder what happens to people afterwards – I mean, when we’ve done our job and the courts have done theirs? Don’t you worry that all you’ve done is make a whole lot of people’s lives even worse? Do you always sleep properly at night, Diane?’

‘Yes, like a log.’

‘I’m not sure I believe you.’

Fry looked at Cooper more closely. ‘Are you all right, Ben? Look, don’t worry too much about John Lowther’s death. You did your best to help him. It was the system that let him down, not you.’

‘There’ll be an enquiry. It might decide that I did the wrong thing. There’s only my word for what happened.’

‘You have a witness,’ said Fry. ‘Georgi was there.’

‘No, he didn’t see what happened,’ said Cooper. ‘I told him to stay back on the stairs.’

Fry looked at Kotsev, who gazed back at her impassively.

‘On the contrary,’ he said. ‘I saw everything.’

‘You can’t have done,’ said Cooper. ‘Georgi, there’s no need –’

‘I will tell the story, if I’m called upon. Ben acted well. He was a hero.’

Cooper flushed, uncomfortable with both the sentiment and what seemed to be Kotsev’s misguided loyalty.

‘Let’s get on with it, shall we?’ he said.

He couldn’t help being sceptical about what Fry hoped to achieve in Matlock Bath tonight. A suspect loose among the crowds, strolling through Derwent Gardens with all these families? It didn’t bear thinking about. The risk to the public represented an operational nightmare.

DI Hitchens had made the right decision, in Cooper’s view. No responsible senior officer would authorize an attempt to carry out an arrest in these circumstances. The most they could do safely was to keep Mullen under surveillance – and even then it would be at a distance. So no heroics. Follow him until he was in a location where the situation could be safely contained. Oh, yes. And pray he didn’t get away again.

‘Oh, and make sure you all stay in touch,’ said Fry. ‘That’s what the radios are for.’

‘Yes, how come you manage to get these radios and ear pieces issued, if we’re here unofficially?’ asked Murfin.

‘Gavin, haven’t you learned when not to ask questions?’

They started from the northern end of the village and separated, taking the riverside walk and the parade of shops in pairs. The village really was getting packed. This was the last night of the illuminations, and the night would climax with a fireworks display from the top of High Tor.

Tomorrow, the Heights of Abraham would close for the winter. The cable cars would stop running, the gift shops would shut, and the terraces of the Hi Café and Summit Bar would be left empty. The clocks went back an hour in the morning, and winter would have arrived.