They looked like good friends. Maybe this girl, whoever she was, could fill in some of the gaps in Miriam Fox's life. We'd have to try to locate her, if she was still around. I put the photos in my notebook and moved over to a battered-looking wardrobe next to the bathroom door.

We went over everything bit by bit. Malik discovered a wad of notes: eight twenties, a fifty (how often do you see one of those?) and a ten. He appeared quite pleased with the find, although I wasn't sure why. A prostitute keeping cash in her flat was hardly a revelation.

'It means she definitely planned on coming back here,' he told me.

I told him that that's what I would have assumed anyway. 'If she picked up a punter and he just turned out to be the wrong sort of guy, then there's no question that she went out intending to come back here. Why wouldn't she?'

Malik nodded in agreement. 'But we're still trying to discover a motive, aren't we?' he said evenly. 'And at least this provides evidence that she wasn't running away from something and got caught before she could escape. It gives more credence to our theory of a dodgy punter.'

Credence. That was an interesting word. Malik was right of course. It did help to close off alternative theories, leaving us scope to focus our enquiries on certain areas, but I thought that maybe he was unnecessarily complicating matters. Malik was trying to look at it from the angle of Sherlock Holmes, and you didn't need to do that. If a prostitute gets her throat slashed and her genitalia mutilated, and her body's discovered on the edge of a notorious red light district with the clothing interfered with, it's fairly obvious what's happened.

Or so I thought.

There was nothing in the wardrobe that told us anything. There were a couple of drawers in there containing various knick-knacks; some books, including two by Jane Austen, which caused me to raise my eyebrows (how many whores read Jane Austen?); a bag of dope; an unopened carton of Marlboro Lights; a jewellery box filled with costume jewellery. Nothing unusual, but no address book or anything like that, which might have thrown up a few clues. The man who'd killed her may well have been one of her regulars, someone who could have been in love with her but whose love was not being reciprocated. Out of frustration, he kills her. Out of rage, he mutilates the corpse. An address book might have contained the details of this man, if he existed. But of course, these days things are a bit different. She might have kept details of her clients in a palmtop PC or on a mobile, rather than writing them down on paper. Obviously, in a block of flats like this you weren't going to keep readily saleable items such as electronic goods on display for your neighbours to pinch, so I presumed if she owned anything like that, and it seemed highly likely that she had, she would have hidden it somewhere in the flat.

'Did she have a mobile on her when they found her body?' I asked Malik.

'I don't think so,' he said, shrugging. 'But I'm not sure.'

I thought about phoning and asking Welland, then decided it would probably be easier just to look for it. I couldn't recall him saying anything about a mobile in the briefing. 'Give me a hand lifting up this bed, will you?'

Malik lifted it up while I peered underneath. Apart from a lot of dust, another book (which turned out to be another Jane Austen), and a pair of knickers, there was nothing there. I stood back up and Malik put the bed down again.

I was wondering where to look next when there was a loud knock on the door. We both stopped and looked at each other. The knocking came again. Whoever was on the other side wasn't particularly patient. I was keen to find out who it was, so I stepped over and opened it before he could knock again.

A stocky black guy, late twenties, was glaring at me. He didn't hang around. 'Who the fuck are you?' he demanded, pushing past me into the flat. He stopped when he saw Malik in his rubber gloves standing by the bed, and immediately twigged. I closed the door to prevent any quick escape. 'You're Old Bill, aren't you?' he added, somewhat unnecessarily.

'While you're here, sir,' I said, walking up behind him, 'we'd just like to ask you a few questions.'

'What's going on?' he asked, whirling round to face me.

I could see him calculating the possible reasons why we were there and whether it was worth him hanging about. It didn't take him long to decide that it wasn't. He shoved me once, very hard, in the chest and made for the door. I stumbled but somehow managed to stay upright. He grabbed the handle, pulled the door open and tried to slam it in my face. He almost got me as well but my reflexes didn't let me down and I managed to dodge it and run out after him, Malik hot on my heels.

I used to be a sprinter when I was at school, and at the age of thirteen I did the hundred metres in 12.8 seconds, but thirteen was a long time and a lot of cigarettes ago.

But I was still quick over short distances and as he rounded the corner and charged down the stairs, two at a time, I was only a few feet behind him. The door was slightly ajar and he pulled it open and kept running pretty much in one movement. But I was closing. As I reached the top of the steps I dived onto his back and grabbed him in a desperate bearhug. 'All right, come on!' I panted in as authoritative a voice as I could muster. But it didn't seem to work. He kept running, at the same time shaking himself out of my grip, and managed to plant an elbow in my face. I yelped but continued chasing, one hand stretched out trying to grab him by the collar, wondering amid the pain in my lungs exactly how I was going to bring this guy to heel.

Suddenly he slowed abruptly, half turned so he was sideways on to me, and brought back his fist ready to throw an almighty punch. Momentum kept me going and, even though I knew exactly what was going to happen, I had no way of stopping it. His fist connected perfectly with my right cheek, sending me completely off balance. My head pounded with the shock of the blow and I bit my tongue as I fell against a wall. My legs wobbled precariously and then went from under me, and I fell backwards onto the pavement, hitting it arse first.

Malik immediately screeched to a halt beside me. 'Are you all right, Sarge?' he yelled with more concern than I would have expected from him.

'Get after him!' I panted, waving him away. 'Go on, I'm fine.'

Which was bullshit, of course. I felt like death. My lungs were bursting and the whole right side of my face throbbed. I opened my eyes and my vision was partly blurred. Still sitting where I'd fallen, I watched as Malik disappeared up the street, all five feet eight of him, armed with nothing more than harsh words. Somehow I didn't think an arrest was imminent.

I was going to have to give up smoking. I couldn't have run much over thirty yards all told and it felt like I'd done a mile at a sprint. The problem with not taking regular exercise, especially when you combine it with a shit lifestyle, is you don't realize quite how unfit you really are. I was going to have to start going back to the gym, even though my membership had lapsed close to two years ago. I couldn't embarrass myself like that again. That cheap piece of dirt, who from the way he acted was no doubt Miriam Fox's pimp, could have kicked the shit out of me if he'd wanted to, the contest was that one-sided.

Across the street I could see a middle-aged woman staring out of her window in my direction. She looked like she felt sorry for me. When I caught her eye, though, she turned away and was gone.

As I gingerly got to my feet, I found myself experiencing an impotent rage. He'd made me look a fool. I wished I'd had the gun I'd been using the previous night on me. I could have blown that fuck apart. I wouldn't even have needed to tire myself out. I could have just strolled down the steps, taken aim at the middle of his back, and fired at leisure. He might have been a solid boy, but I'd yet to come across anyone whose skin deflected lead.