‘By pressing the button?’

‘Yes.’

‘Did you realize that it only tests the sound of the alarm, not whether the detector itself is functioning?’

Mullen looked paler than ever. ‘No, I didn’t know that.’

Fry watched him for a few moments, but felt no nearer to getting inside his mind.

‘I’ll give you a lift to Darley Dale,’ she said. ‘That’s where you want to go, isn’t it?’

‘Yes, to my parents-in-law.’

When she’d got him in the car, Fry let him sit quietly for a while as they drove across Edendale. Many people would feel uncomfortable with the silence and want to make conversation. But not Brian Mullen. She left him to stew until they were out of town and heading towards the A6.

‘Tell me about the arguments you’d been having with your wife,’ she said.

‘What arguments?’ said Mullen.

‘According to your neighbours, there had been several rows between the two of you in recent weeks.’

He shook his head. ‘We had a row about the new carpet, that’s all. I didn’t think it was the most practical thing with three kids in the house. And I didn’t like the idea of Henry buying things for us all the time, either. I told Lindsay I could support my own family without his help.’

‘Yes?’

‘But she got her own way in the end. She could never say no to Daddy when he wanted to give her something. So it wasn’t much of an argument.’ Mullen twisted in his seat to look at her. ‘Is that what you meant?’

‘And the rest.’

‘No, no. We never had rows, as a rule.’

‘That’s not what I heard.’

‘Well, you’ve got it wrong.’

They entered Bakewell, and Fry had to concentrate as she negotiated the narrow streets and the busy roundabout in the middle of town. She was able to relax again as they approached the entrance to Haddon Hall. But there were only a few miles left now.

‘You told me earlier that Lindsay and her brother were very close,’ she said. ‘That can be a difficult relationship for a husband to deal with sometimes. How do you get on with John Lowther?’

‘Fine. Just fine.’

‘Not even a hint of jealousy, perhaps? If John bought presents for your children, it would be natural for a bit of resentment to creep in.’

‘Any resentment wasn’t on my side,’ said Mullen.

‘Ah. So you think your brother-in-law begrudged someone coming between him and the sister he was so close to? I can see how that might cause friction in the household. Did your arguments concern John?’

‘You’ve still got it wrong. And whoever told you that has got it wrong, too.’