As soon as Cooper walked back into the office at West Street, Fry slammed the phone down and glared at him. ‘See, I took my attention off Brian Mullen. I let him know he was under suspicion, and then allowed him the chance to do a runner. I should have been completing the case against him by now so we could make an arrest. But I was distracted. Too much attention on the Rose Shepherd enquiry. How can anyone be expected to do two jobs at once, and do them properly?’

Fry paused, and looked at Cooper. He didn’t answer her, but she didn’t expect him to. He was only there for her to have someone to sound off at. Fortunately, he was good at that.

‘What’s happened, Diane?’

‘I need to talk to Brian Mullen again,’ she said. ‘He should be with his parents-in-law in Darley Dale, but they say they don’t know where he is today. And he has Luanne with him.’

‘That’s bad news.’

‘Bad news? It’s a total disaster. I’m sending Gavin out to speak to John Lowther, and to anyone else who might know where Mullen is. But I’ve a nasty feeling he’s done a runner.’

‘Are you still fancying Mullen for the arson? What would his motive have been?’

‘He and Lindsay had been having blazing rows. Loud ones, by all accounts. Their neighbour Keith Wade heard them arguing earlier that evening. The parents are being cagey on this one, so I don’t know how serious their marital problems were, but they could have been on the point of splitting up. Lindsay might have threatened to walk out on Brian, and told him he’d lose the children. That would have hit him pretty hard, I think.’

‘Oh, so he killed them?’

‘It happens, you know – some distraught dad decides to end it all, and take the family down with him.’

‘But Brian Mullen didn’t do that, did he? He was the one who survived.’

‘Well, he could have chickened out at the last minute. Once he saw the flames and felt the heat, and realized what he was doing.’

‘I suppose that’s possible.’

‘You sound doubtful. Tell me – you always seem to have some theory of your own that doesn’t fit with anyone else’s. Are you going to share it with me, Ben?’

Cooper shook his head. ‘I don’t have a theory. It’s just that . . .’

‘Yes?’

‘Well, if what you’re saying was really the case, I’d expect Mr Mullen to be consumed with guilt right now. He’d be thinking that he ought to have died in the fire with his family, and blaming himself for his cowardice in not going through with it.’

‘That would explain his present attitude, wouldn’t it?’

‘No, I don’t think so, Diane. It doesn’t feel right.’