Caz closed her eyes, and appeared to be counting. ‘We’d have found it on the body,’ she grated. ‘And where do you think these cameras would have been hidden? Apart from anything else, it’s illegal to watch people surreptitiously. All cameras have to be clearly visible.’

‘Well, I don’t imagine they’d be worried about legality, would they – if they were planning to murder somebody? That’s illegal as well, isn’t it?’

‘Okay. I’ll admit it’s technically possible.’

‘And it was you who said he – they – must have been watching for me to leave,’ Thea reminded the detective. ‘How did you think they were doing it?’

Caz shook her head. ‘We’re agreeing, then, aren’t we. And we both probably think it’s more likely it was just luck that you were out at the time. If you’d been there you might have been killed as well. Have you thought of that?’

‘Not very seriously. I’ve been assuming that Grace was very much the target, for some very specific reason.’

‘There’s not much evidence for that.’

‘Yes, there is.’ It felt important to Thea to argue this point. ‘She was scared of being found. She’d left all her personal possessions somewhere, in case she could be traced through her phone. She was tired out. Any other scenario implies a homicidal lunatic, just randomly killing women in houses for the fun of it.’

Barkley shook her head. ‘That’s not what I said. I agree that Grace was the target – but if you’d got in 220the way, you might have been collateral damage. The phone thing doesn’t cut much ice. Ordinary citizens can’t trace a person through their phone. You’ve got to get a warrant and wait for the provider to co-operate.’

‘Oh.’

‘No, the problem is there’s absolutely nothing to go on. There’s no useful footage from the business park, either. There are plenty of blind spots where a car could park and somebody get out and run off without being caught by the cameras. Again, we haven’t got the resources to check the owner of every single car coming in and out on Saturday morning. It’s possible in theory, but much too labour-intensive.’

Thea frowned sceptically. ‘Surely it’s not that hard? There can’t have been so very many, after all. Check the registration numbers against the DVLA records, and flag up anything that doesn’t belong to anybody who works or lives there.’ She paused. ‘Well, I guess there are various sorts of customers as well. I can see it would take some work. But the camera shows the people inside the car as well, doesn’t it? Check the ones with small dark females in them. There might only be one or two.’

‘They don’t show the people inside,’ said Barkley tiredly. ‘You get a glimpse of the driver, usually in profile, but not much more than that.’

‘Well, I still think there’s a whole lot of evidence you could find. Somebody who lives or works in one of the businesses must have taken Grace there in a car on Saturday. I bet there’s some nasty illicit business going on behind an innocent front. That’s not impossible, is it? 221She was very obviously oriental, even if her father was British. She must have stood out.’