The last stop was on the fringes of Burnage, but this time it was a between-the-wars semi that looked completely dilapidated. There was grass growing through the gravel, the gate was hanging from one hinge. So much paint had peeled off the door and window frames it was a miracle they hadn't dropped to bits. Two men were working on the roof, replacing broken slates and pointing the chimney stack. Lomax got out of the Jag and shouted something to the men. Then he took a pair of overalls out of the boot, put them on over his jeans and sweatshirt and walked into the house. A few minutes later, I heard the high whine of a power drill. I decided I could use my time more fruitfully back in the office with the computer files.

Shelley was on the phone making 'new client' noises when I walked in, but judging by the speed with which the coffee appeared on my desk, she'd already had the run-down on my success with Ted's conservatories. 'Good news travels fast, huh?' I said.

'I don't know what you mean,' she said haughtily. 'Have you done the client reports for PharmAce and Ted Barlow yet?'

I took the cassettes out of my handbag. 'Voila!' I said, handing them over with a flourish. 'God forbid we should keep Ted waiting. How is he, by the way? Happy as a sandboy?'

'As if it isn't bad enough spending my days with someone who thinks she's a genius, I now have to listen to Ted Barlow telling me you're a genius. The bank's agreed to restore his loan and his access to their financial services division, and he's got an advert in Monday's Evening Chronicle for a new sales person. The police raided the three houses last night and got enough evidence to arrest Jack McCafferty and Liz Lawrence. They should both be charged later today, and Ted's completely in the clear,' Shelley said, unable to keep the smile out of her eyes.

'Great news. Tell me, Shelley, how come you know all this?'

'Because it's my job to answer the phone, Kate,' she replied sweetly. 'Also, I've had calls from a DCI Prentice, a woman called Rachel Lieberman, Alexis Lee and four calls from Richard who says he doesn't want to trouble you but have you charged the battery on your mobile because it's not responding.'

I knew there had to be a reason why I'd had peace all morning. I'd remembered to charge the phone up overnight. I'd just omitted to make sure it was switched on this morning. Feeling like a fool, I smiled sweetly at Shelley. 'I must have been in one of those black holes when he tried me,' I said.

Shelley gave me the look my mother used to when I swore blind I'd not eaten the last biscuit. 'If you're having that much of a problem, maybe we should just send it back,' she said.

I bared my teeth. 'I'll manage, thanks. So now he's got that load off his mind, how's Ted? Able to devote one hundred per cent of his attention to helping you achieve the full potential of your house?'

'Have I ever told you what a blessing it is for me to work with you, Kate? You're the only person I know who makes me realize just how mature my two kids really are.' She turned and headed for the door. I poked my tongue out at her retreating back. 'I saw that,” she said without turning her head. At the door, she looked back at me. 'Joking apart, it's OK.' Then she was gone, leaving me alone with the laptop and my phone messages, which I chose to ignore.

Now I'd worked out what the RV directory was all about and I'd actually seen some of the properties in question, I had to unravel the contents of DUPLICAT. At first sight, they seemed to be completely innocuous. They were files relating to the purchase of various properties by assorted individuals and the mortgages that had been arranged for them. The material seemed exactly the same sort of stuff that was in the unprotected WORK.C directory. The only difference was that in DUPLICAT, every single mortgage lender was different. In the few instances where the same building society had been used more than once, Cheetham's clients had chosen different branches.

It was only when I'd worked my way through to the most recent of the files that something finally caught my eye. Even then, I had to look twice and cross-check with another file to make sure it wasn't just boredom and tiredness that were tricking me. But my first reaction was right. The property in the file was a detached house on an exclusive development in Whitefield. But another couple had arranged a mortgage on the same property and their address was none other than the dilapidated semi I'd left Brian Lomax working on.

I could feel a dull ache starting at the base of my skull. The combination of staring into my laptop and trying to work out what was going on was getting to me. I stood up and stretched, then moved around the office doing some of the warm-up exercises I'd learned down the Thai boxing gym. I swear the routine sends my brain into an altered state. As my body found its rhythm, the tension flowed out of me, and my mind went into free fall.

Then all the assorted bits and pieces of information that had been swilling round in confusion inside my head came together in a pattern. Abruptly, I stopped leaping around the room like Winnie the Pooh's imitation of Mikhail Baryshnikov and dropped into my chair. I didn't have a split screen facility on the laptop, so I hastily scribbled down half a dozen of the addresses of the houses that had been mortgaged according to DUPLICAT, along with the names of their buyers. Then I called up the files from WORK.C, the directory of Cheetham's straight conveyancing business.

It didn't take me long to discover that for every file in DUPLICAT there was another file in WORK.C that corresponded to it. In each case, the house was the same but the buyers and the mortgage lenders were different. Now I understood exactly what Brian Lomax and Martin Cheetham had been up to. They'd exploited the system's weaknesses in a scam that would have given them a tidy profit almost indefinitely. The pair of them were committing the classic victimless crime. But someone had grown greedy, and that greed had led to Martin Cheetham's death.

I glanced at my watch. It was just on four. I still had no proof that Brian Lomax had been an active conspirator rather than a mug that Martin Cheetham and, possibly, Nell Lomax had exploited for their own ends. But I was convinced that whatever had gone wrong with Cheetham's carefully worked out scheme could be traced straight back to Lomax. There was something about his body language, a kind of swagger in the way he carried himself. Brian Lomax was no more one of life's victims than Warren Beatty. And I had to get him in the frame before a jumbo jet took off into the sunset on Monday night.

I closed the laptop and took it through to Bill's office. He was staring at an A4 pad, gnawing the end of a pencil. 'Bad time?' I asked.

'I'm trying to write a memory resident program that will automatically check for any date-activated programs hiding in the computer's memory,' he said. He dropped the pencil with a deep sigh and started chewing his beard instead. I'm often tempted to ring his mother and ask what experience he had in his infancy that's made him so oral.

'Virus protection?' I asked.

'Yup. I've been meaning to get to it since the debacle on Yom Kippur, but this is the first chance I've had.' He pulled a face. Bill was still smarting from the computer virus that had attacked one of our clients at the beginning of October. The virus had been set to activate itself on the Jewish Day of Atonement. Our clients, a firm of accountants called Goldberg and Senior, had taken it very personally when all of their records had been turned into gobbledygook. They didn't find it a consolation when Bill told them it was a one-off that wouldn't recur in other years, unlike the really vicious Friday the Thirteenth and Michelangelo viruses that attack again and again till they're cleansed for good.