Mullen controlled his burst of anger, then raised his still bandaged hands, as if presenting the evidence.

‘And you can’t remember what you burned yourself on, Mr Mullen?’

‘I told you, it was the banister rail. It must have been that, because it was the only thing I touched.’

‘Ah, yes. And it’s made of wood, so it would have been burning, or at least smouldering. But the banister rail is only on one side of the stairs – the other side is a blank wall. Would you have touched the banisters with both hands?’

‘I must have done.’

Mullen held up his hands again, as if he thought she couldn’t see them. The facts were indisputable, he seemed to say.

Fry wished she could have taken swabs from his hands to test for traces of accelerant on his skin, but she had no evidence to push it so far. And it was too late now anyway.

‘Look, maybe I panicked and touched it with the other hand on the way down,’ said Mullen.

‘It’s possible.’

‘Of course it is.’

‘And you didn’t go into any of the rooms downstairs?’ asked Fry. ‘The sitting room, for example?’

‘No. Why would I do that? Like I told you yesterday, I knew my family would be in bed at that hour.’

‘We believe the fire started in the sitting room. It must have been obvious when you entered the house that the smoke was coming from there. Are you quite sure you didn’t go into the sitting room, or even touch the sitting-room door?’

‘Yes, I’m sure.’

Mullen was starting to look sulky and irritable. Fry gave Cooper a look that told him to take over for a while.

‘Do you smoke, sir?’ asked Cooper.

‘No.’

‘What about your wife? I’m sorry to ask –’

‘No, Lindsay didn’t smoke either. I can see what you’re driving at, but we both agreed not to smoke a long time ago, for the sake of the kids. Passive smoking is very damaging to young children. Their air passages are so small they breathe in far more smoke than an adult would.’

‘I see. What about other members of your family?’

‘There’s only John who’s ever smoked. But he knows not to when he’s in our house . . .’

‘. . . for the sake of the kids, yes,’ said Fry.

Cooper consulted the notes Fry had given him. ‘John? That would be John Lowther, your brother-in-law?’

‘Yes.’

Fry noticed a nurse hovering in the background. ‘We’ll let you rest now, Mr Mullen. I realize you’ve had a terrible ordeal, and we appreciate your time and co-operation.’

‘It’s OK. Obviously, I want to help. I mean, it was my wife and kids who got killed in that fire. If some bastard –’