To Fry’s amazement, he lay down on the floor and demonstrated what it was like to be dead. She’d never seen anybody look less dead in her life. But if there had been a weapon handy, she might have felt tempted to help him achieve authenticity.

Then he opened his eyes and looked up. ‘We used to say you had seven minutes to get out of a burning building. Now, with all the materials we’ve put inside them, it’s more like three minutes.’

‘And that’s why we advise people to install smoke alarms.’

‘Ah, yes. The smoke alarm. Pity about that.’

‘It was functioning, wasn’t it?’

‘After a fashion.’

‘Mr Mullen says he tested it regularly.’

‘No doubt he did. But, like most people, all he was doing was pressing the button. That proves the sound works, and the batteries aren’t dead. It doesn’t tell you whether the detector is functioning.’

‘What are you saying?’

‘I took a look at the smoke alarm earlier. And I’d say your Mr Mullen never bothered reading the manufacturer’s instructions. He should have vacuumed around the detector regularly to prevent the build-up of dust. Apart from battery failure, there’s nothing worse than accumulated debris for interfering with an alarm. This one hadn’t been cleaned for a long time. There was even a thin layer of cement and plaster particles, so I’m guessing the family had building work done in the kitchen at some time.’

‘Yes, they had new units put in about six months ago, and an extractor fan installed.’

‘There you go, then. Cement and plaster, with a couple of layers of dust. It was almost as if they’d built a wall inside the detector. I’m sorry for the chap, and all that. But facts are facts.’

‘What about where the fire started?’

‘Now, that’s interesting,’ said Downie. ‘The point of origin would normally be near the area of greatest damage. But there are three items of furniture in this room with differing upholstery. The nature of the upholstery makes a big difference.’

‘Do you mean polyurethane foam?’

‘Well, all three items contain polyurethane foam padding. It’s the covering that matters. Anyway, it appears to me that the initial fire was started by applying flame to a quantity of papers adjacent to this chair here, right among these toys.’

‘But the other chair seems to have suffered most damage. That, and the settee.’

‘It’s rather deceptive at first glance, isn’t it? You see, the chair this side of the room is upholstered with a thick cotton weave. It was probably a nice piece of furniture.’ Downie moved across the room. ‘The settee, on the other hand, was padded with polyurethane foam and covered in a partly synthetic fabric mixture, probably poly-cotton. Now the third item of furniture. This, I’m afraid, is a cheaply upholstered armchair, with a wholly thermoplastic cover over polyurethane foam, without any inter-lining.’

‘So the quality of the furniture varied. Perhaps the Mullens should have gone to Ikea and bought a complete suite. But they probably couldn’t afford it.’

Downie didn’t seem to hear her. ‘You see, despite the fire having been lit directly adjacent to it, the cotton-weave chair sustained less damage than the other two items. The natural fibre cover charred and pyrolized, but the weave didn’t fall away, so it provided some retardation of heat release. However, the cheaply constructed armchair was completely consumed, and the synthetically upholstered settee was also severely damaged. Both would have been ignited by radiated heat. The thermoplastic material melts and falls away to expose the underlying foam to the fire. Not so good.’

‘I think I see,’ said Fry, surprised to realize that she actually did.

‘Excellent,’ said Downie. ‘Well, that’s my theory for now. I’ll examine remaining fabric from the three items and test their burning characteristics. But the carpet is probably going to be most helpful to us. Carpet absorbs accelerant well, and retains residue longer.’

Petty had moved into the sitting room and was concentrating her attention on a heavily damaged area of carpet.

‘Is this where the accelerant was used?’

‘We think so. It’s one of the sites identified by the dog.’

Petty was photographing the burn pattern before she began to cut into the carpet. She rolled up a sample with the foam backing on the inside and eased it vertically into a container.

Fry left the house to look outside. Someone was bound to have left their fingerprints somewhere in the house, in an area undamaged by the fire. The trouble was, it might well be a firefighter or a police officer. Not to mention members of the household and their various friends and relations. The footwear impressions were going to be useless, too. The layer of mud wasn’t deep enough, and the lab would never get a match, or identify a pattern.

She watched Downie carefully placing his evidence samples and control samples separately in his van. And she saw that he’d completed the most important items of all – the chain of custody forms.

Then she spotted Wayne Abbott standing in the road near one of the Scientific Support vehicles and walked across to him.

‘Is there any particular reason we got Liz Petty?’ she asked him.

Abbott turned in surprise, and she saw that he had a mobile phone pressed to his ear. ‘Hang on a minute,’ he said, and held the phone away to free both ears. ‘What was that?’

‘I wondered how we came to get Liz Petty,’ said Fry.

He stared at her, reflecting her hostility like a mirror. ‘Liz attended an inter-service fire investigation course at Ripley not so long ago. She was the obvious choice for this job. Why?’

‘Oh, no reason.’

‘She was up to her neck in volume crime, dealing with burglaries on the Southwoods Estate,’ said Abbott. ‘But we gave this priority for you. What’s the problem?’

‘Nothing.’

Abbott turned his back and resumed his phone call. ‘Sorry … no, it was just someone wasting my time.’

14

Hitchens was waiting for Cooper and Murfin in the garden of Bain House. ‘The chiefs are talking about bringing in the NCOF,’ he said.

Murfin looked puzzled.

‘The National Crime and Operations Faculty,’ Cooper told him quietly.

‘That must be at Bramshill – Acronym City.’

‘Yes.’

‘If Mr Kessen puts in a request, their regional officer will provide us with assistance. In fact, the NCOF can turn out a full team. Their own SIO, psychologist, forensic scientist, pathologist –’

‘With respect, sir, we don’t need all that.’

Hitchens looked at Cooper and smiled. ‘That’s what I think, too. But let’s prove that we don’t need it, shall we?’

‘I don’t think it will be much use to us, sir,’ said Cooper as he followed the DI into the house, ‘but I’ve asked for footage from the Matlock Bath webcam for Saturday afternoon. They were very helpful. They’re sending me a QuickTime movie file.’

‘OK, Ben. Well done. We have to try everything.’

DCI Kessen was sitting in an armchair in the sitting room of Bain House, looking thoughtfully at the white and grey walls.

‘How do you think the victim would have spent her time, all alone in this house?’

‘Well, there are two TVs,’ said Hitchens. ‘One in the sitting room, another in the kitchen. Also a couple of radios, including a digital on the bedside table. When we turned it on, it was pre-tuned to BBC 7.’

‘Sorry, I haven’t gone digital yet. You’ll have to enlighten me.’

‘Re-runs of old BBC comedy shows and dramas. You know, Hancock’s Half Hour and Round theHorne.’

‘OK.’

‘There’s a decent stereo system, too. Nothing special – but women don’t care much about the technical details, do they? She obviously used it, because it was plugged in and switched on, just left on standby. And there was a CD in the slot – an Abba compilation.’