‘Has Brian got the baby with him? Luanne?’ he said.

‘We believe so, sir.’

‘Shit. I hope you find them.’

‘So do we.’ Fry paused. ‘Speaking of Luanne, we know about the adoption. Mr Mullen’s father-in-law has explained to us that Brian and Lindsay couldn’t have any more children, because Brian was infertile after a bout of mumps.’

‘Mumps?’ said Skinner. ‘Is that what he told you?’

‘Certainly. He said the illness caused physical damage that made Brian become infertile.’

‘Well, it’s not what Brian told me at the time. Mumps had nothing to do with it.’

‘So what was it, then?’

‘STD.’

‘A sexually transmitted disease?’

‘That’s right. I can’t remember the exact name, though. Something with “clam” in it.’

‘Do you mean chlamydia?’

‘Yes, that’s what Brian had. And it wasn’t the first time, either. Chlamydia was what caused the damage. He told me all about it. If you get it too often, it causes scarring and blocks the – you know, the passage.’

Fry stared at him, her mind adjusting to a series of new possibilities. ‘Not mumps?’

‘I wonder if mumps was what he told his in-laws,’ said Skinner. ‘I met Henry Lowther once. He’s the sort of bloke who likes everything to seem right and proper. Even his son-in-law – since he’s stuck with him.’

‘Does Brian not get on with the Lowthers?’

‘Well, you know what it’s like. He wasn’t really good enough for their daughter from the start. They’d have preferred Lindsay to marry someone loaded. A step up on the social scale, if you know what I mean. Not a few steps down, like Brian.’

‘Mr Skinner, were you aware of any problems in the Mullens’ marriage? Was there any trouble between Brian and Lindsay?’

‘Trouble? Why should there be?’

‘Well, for a start, I presume Lindsay knew about the chlamydia? That would make quite a difference to their relationship, I think.’

The idea seemed to strike Skinner for the first time. ‘You think she might have blamed Brian for the fact that they couldn’t have another child naturally? Lindsay really, really wanted a daughter, you know.’

‘Yes, I know that.’

Skinner nodded. ‘That would make her a bit upset with him, I suppose.’

‘Well, yes,’ said Fry. ‘And there are other things that might have upset her, too – like where her husband picked up an STD in the first place.’

‘Hey, you’re right. I imagine there were a few words exchanged.’

‘But Brian never mentioned anything like that to you?’

‘Do you know, there were times when he was a bit pissed off, and I reckoned he might have had problems at home. But he never explained why – we didn’t talk about things like that.’

Fry cursed to herself as she left Jed Skinner and got back in the car. Male friends, what a waste of time. To learn anything about the state of the Mullens’ marriage, she needed to talk to Lindsay’s mother. But she didn’t give much for her chances of getting information out of Mrs Lowther right now.

With a frown, Fry turned to her notes from the interviews with Brian Mullen, seeking the smallest clue. After a few minutes, she picked up the phone and called Cooper.

When his phone rang, Cooper was standing by the lid of a shaft into the hillside that had been sealed by a steel grille. A bush rustled, showering drops of moisture, and a small, grey shape slipped along a branch, stopping to pull off the berries.

‘Ben, what are these illuminations that Brian Mullen mentioned?’

‘Illuminations?’

‘I’m sure he said they were in Matlock Bath. The only illuminations I know of are in Blackpool.’

‘Well, they’re not quite the same. In Matlock Bath, there are some lights along the promenade and across the river, but when people talk about the illuminations they mean the parade of boats.’

‘Boats?’

‘They create designs out of lights and mount them on rowing boats. Then they parade up the river – when it’s dark, of course. So what you see isn’t the boat but something like, say … an illuminated London bus floating on the water. There’s other stuff, too – fireworks, entertainment. You can see it all from the pleasure grounds in Derwent Gardens.’

‘OK. So when does this happen?’

‘September and October, but only at weekends. They call them Venetian Nights. I don’t know why, it must be something to do with the boats. But they always attract big crowds. Why, what are you thinking?’

‘Brian Mullen. When I interviewed him in hospital, he said that he and Lindsay had promised to take Luanne and the other children to see the illuminations in Matlock Bath. It was supposed to be a special treat.’

‘Yes, but surely he’d have more sense than to …’

Cooper stopped speaking, and Fry laughed. ‘What was it you were saying earlier, Ben? About people acting in an irrational way?’

‘Emotions interfere with rational behaviour.’

‘That was it.’

‘Diane, why were you so sure about Mr Mullen being involved in the fire?’

‘He never seemed particularly grief stricken to me. Some of those people leaving flowers outside the house looked more upset than Brian Mullen did.’

‘He was probably in shock, Diane. Besides, a public show of emotion is unnatural for some people. He could well have been suppressing it while he was in hospital. Being discharged and coming home would be the time when the truth hit him hardest, don’t you think? I mean, finding just Luanne waiting for him, and knowing that he’d never see the rest of his family again. There must have been a moment when he couldn’t suppress the knowledge any longer. That would be when his world caved in, I imagine. If he talked to a counsellor at the hospital, he was probably warned about that.’ Cooper gazed down at the cap of the mine shaft thoughtfully. ‘Although I’m not sure when that moment would be – because Mr Mullen didn’t actually go home, did he? He went to his in-laws’ house when he left hospital.’

‘No, you’re wrong. He did go home,’ said Fry. ‘I took him there.’

Cooper paused. ‘Oh. So you did.’

‘I wanted him to see the house after the fire.’

He hesitated for a moment, wondering what the right thing was to say. ‘Well, it wasn’t your fault, Diane.’

She was silent for so long that Cooper thought her mind must have switched to a different subject altogether, the way it sometimes did. And when Fry did speak, he still wasn’t sure whether that was the case, or not.

‘Thanks a lot, Ben,’ she said at last.

And then she was gone, and Cooper was listening to the faint hiss of his phone.

A second later, Georgi Kotsev emerged from a summer house a few yards up the steep path. The building was made of tufa, with a thatched roof.

‘I don’t see him,’ said Kotsev. ‘What is this place anyway?’

‘A tourist attraction.’

‘OK, I believe you.’

‘When we’ve finished, we can walk back to the village, if you’re too scared of the cable car. All we have to do is press a button to release an automated gate near West Lodge.’

‘Let’s keep looking.’

Cooper followed Kotsev up the path. Next summer, he ought to bring Liz up here. They could have a goat’s cheese panini or a tuna melt in the Hi Café, or sit on the terrace of the Summit Bar with a table among the flowers, overlooking Matlock Bath.

That was assuming they were still together next summer, of course. He’d never gone out with anyone for as long as twelve months before.

For a moment, Cooper turned to look back through the trees at the view down into the valley. He recalled that the white building near the tavern was Upper Towers, where beer had once been served to lead miners. Inside, it had round rooms, so they said.

‘Hey, here!’

Cooper spun round and found Kotsev standing with a Heights of Abraham employee in a high-vis jacket.

‘Have you got something?’

Kotsev pointed up the hill. ‘He’s at the tower.’

The burnt-out Shogun was in the garage, covered in a tarpaulin. Wayne Abbott greeted Fry and Hitchens with a clipboard in his hand.