‘A webcam. You can go on the internet and see a view of Matlock Bath promenade. I think they have it running pretty much every day.’

‘Who operates this thing, Cooper?’ asked Kessen, leaning forward in his chair.

‘I think it’s a photographic museum.’

‘Time lapse, I suppose?’

‘Yes, sir. But no worse than most CCTV systems.’

‘It would be too good to be true if it caught Rose Shepherd. But let’s check it out anyway.’

Hitchens waited to see if the DCI had finished. ‘Next thing,’ he said. ‘We’ve had the victim’s phone records checked, and we now know that a call was made to Miss Shepherd’s home number at three o’clock on Sunday morning. The call lasted only twelve seconds. As you might have guessed, the caller used an unregistered pay-as-you-go mobile. No account, no address. If our suspects knew what they were doing, they’d have bought a phone specifically for this one call, then dumped it. And it looks as though they knew exactly what they were doing.’

‘Pay-as-you-go phones,’ said someone gloomily. ‘The biggest gift that was ever made to drug dealers.’

‘And paedophiles. And terrorists. We need some legislation on this one, don’t you think, sir?’

‘That’s way above our heads, I’m afraid.’

‘Right. We’re just the poor buggers who have to pick up the pieces.’

Hitchens sighed, and departed from his notes. ‘Actually, true anonymity is hard to achieve these days. We might not be able to identify the purchaser of a prepaid mobile, but if the call credits are paid for by card or cheque, the payments can be traced back. Also, we can track the phone’s physical location, provided it’s switched on. But, in this case, assuming our suspects do still have the phone, it’s been switched off since the call to Miss Shepherd.’

‘Dumped it, like you said, sir.’

‘Exactly. Now for the victim’s background. You’re probably aware that this is proving a real headache. Whatever her reasons, Rose Shepherd went to extraordinary lengths to protect her privacy. She left almost nothing of a personal nature to give us an angle on her life. However, we’ve had time since yesterday to go through her cheque books and bank statements.’

‘Anything interesting?’

‘To be honest, I’ve never seen such a boring credit card statement as hers. I was hoping for something a bit revealing – I don’t know, a purchase of expensive wine, or a subscription to a porn website. But nothing out of the ordinary. Not a thing. Her bank statements show her Council Tax, electricity bill and water rates going out on direct debit. Her BT phone bill was paid online by credit card. There’s nothing here that tells us anything about her. All the evidence we have points to Miss Shepherd being a model citizen, paying her bills on time, being no trouble to anyone.’