‘Admittedly, we haven’t traced the driver yet. But even if we do, there was plenty of time for Mr Mullen to start the fire, get clear of the area and catch a taxi back again, arriving when the blaze had taken hold. Then he could draw conspicuous attention to his arrival by doing his tragic hero act in full view of the neighbours. Not to mention the police and firefighters, who were bound to hold him back, so he wouldn’t have to be too much of a hero.’

‘What if he’d timed it wrong, and arrived before the fire crews?’

‘It was a small gamble. Perhaps he had trust in the emergency services. Or perhaps he had more faith in his neighbour spotting the smoke.’

‘OK, it’s possible.’

‘I’ve also taken possession of the clothes Mr Mullen was wearing on the night in question. With your permission, I’d like to get them to the lab.’

‘You’re hoping to find traces of accelerant on his clothing?’

‘Yes, sir.’

‘What about motive?’

‘If the marriage was in trouble, I’m thinking it might have come to a head recently. For example, if Mrs Mullen had told him he had to move out, or she was filing for divorce, he might have been upset about her taking the children away. It’s happened before.’

Kessen nodded. ‘The dog in the manger mentality: “If I can’t have the children, you’re not having them either.”’

‘Yes, sir. There’s one interesting fact from the FSS fire investigator, Quinton Downie. He says the fire wasn’t started in any of the logical places for a random arson attack. Rather, it began where the children’s toys were stored in the sitting room. Apparently, accelerant was poured over them, as well as on the carpet. That might prove to be significant. It makes the attack seem very personal.’

‘And it was carried out by someone who was able to get access to the house.’

‘Yes. I’m not convinced by the side window being forced. There are no signs of entry inside the room. It’s a kitchen window, and I’d expect to find marks on the window ledge or the work surfaces, but nothing’s been disturbed. The kitchen looks positively pristine.’

‘Footwear impressions outside?’

Fry shook her head. ‘Not after the firefighters had done their bit.’

The DCI looked thoughtful for a moment. But he wasn’t a man to take long over a decision.

‘OK. It sounds as though you’ve done all the right things, Diane. We’ll review the enquiry again as soon as you’ve got some forensic reports. I’ll be your SIO for now, so make sure you keep me up to date with any developments.’

‘Thank you, sir.’