'Frank Black. Black's Office Supplies. I'm actually returning her call. She was interested in some prices.'

'Can I put you through to her assistant, Sara?'

'Well, it's actually Miss Graham I need to speak to. Do you know when she's back?'

'I'm afraid she won't be in until tomorrow now. She's at a seminar this afternoon.'

I said I'd phone back, and hung up. After that, I tried Len Runnion's number again, but there was still no answer.

I went back into the bar, took a stool facing the wall near the door, and drank my drink. A mirror stretched right around the wall at head height, and my reflection stared back at me mournfully. I looked a mess, mainly because I hadn't shaved that day, which was deliberate. I was growing a beard now, in keeping with my passport photo. I was also going to have to fatten up a bit. I'd been at least half a stone heavier in the photo, and to be on the safe side I wanted to add another half stone on top of that. I'd had a McDonald's for lunch, which had been a good start, but I was going to have to have a similarly fatty supper for it to have any effect. From now on I was on a diet of greasy, bad food in large quantities until further notice. And I'd probably be one of the first people in the world to actually benefit from it.

I felt like I needed Dutch courage for what I was about to do, so I ordered another pint and drank that with a couple of cigarettes and a bag of cheese and onion crisps I didn't want but felt sure I ought to have. By the time I'd finished it, the predicted after-work crowd had materialized and the bar was three deep with loud, suited individuals and young secretaries out for a good time. The clock above the bar told me it was twenty past five.

Outside, darkness had long since fallen and the streets were crowded with commuters and early Christmas shoppers. The day after tomorrow would be the first of December. The year had gone fast, as they always seem to do. This time, however, I'd be glad when it had been and gone. Memorable it might turn out to be, but for all the wrong reasons.

By the time I got back to the car it had started raining. I jumped in and fought my way through the crawling rush-hour traffic, hoping that I got to Carla's flat before she did. My plan was to wait outside until she arrived, then apprehend her at the door. I'd try to get inside through charm alone – I didn't want to cause a scene – but if she didn't want to play ball, I'd pull the gun I'd taken ownership of the previous night. I didn't think she'd argue with that. After that, I'd play it by ear.

But the traffic was a lot worse than I'd expected and I wasn't totally sure of my bearings, so it was well gone six when I pulled into Carla's cul-de-sac. I managed to squeeze into a parking space about twenty yards down from her building and cut the engine. I could make out her flat through the outstretched skeletal branches of a beech tree. There were several lights on. So she was home.

I cursed silently. I should have got there earlier rather than dawdled over my pints. Now it was going to be difficult to get inside. I lit a cigarette and weighed up my options. I didn't think she'd let me in if I rang on her buzzer. We'd hardly parted on the best of terms, and she had no reason to talk to me. What was I going to say? That I wanted to come up and accuse her of murder for a second time? Breaking in was another option, but I remembered the building's security system being fairly elaborate. The door had been new and the lock was a five-bar. I didn't think my housebreaking skills stretched to that, not without equipment.

Which meant waiting for an opportunity to present itself. I finished the cigarette, took a swig from a bottle of Coke I'd brought with me, and lit another cigarette, wondering what I was going to do when and if she admitted her part in the whole thing. I could hardly make a citizen's arrest, not in my position, and I didn't think I had the stomach to kill her in cold blood. Which kind of cut down my options. Yet somehow I still felt that I was doing the right thing by coming here. That I had to get to the bottom of this before I could continue with my life.

I think I'd been there about ten minutes, maybe a bit less, when a car drove into the cul-de-sac looking for a parking space. I slid down in my seat, not wanting to draw attention to myself, and the car continued past. When it got to the end it made a torturously slow U-turn in the limited space available and drove back out again. About a minute later, I saw the driver, a middle-aged businessman, walk past on Carla's side of the road. He stopped when he came to Carla's building and fished about in his coat pocket for his keys.

I stepped out of the car and crossed the street as casually as possible, coming up behind him as he was mounting the steps. He heard my footfalls and whirled round, his face etched with the automatic fear city dwellers always experience when someone approaches them from behind at night. His expression eased a bit when he saw it was a man in a shirt and tie, but remained suspicious nevertheless.

'Yes. Can I help you?'

I pulled out my warrant card and showed it to him. 'I'm here to see Miss Carla Graham,' I said authoritatively, looking him right in the eye. 'I understand she lives on the top floor.'

He put his key in the door. 'That's right. Well, you'd better buzz her-'

'I'd rather she didn't know who it was, sir. You see, I'm not one hundred per cent sure she'll want to speak to us.'

He looked at me curiously but decided in the end that I was probably who I said I was, and turned the key in the lock. 'I assume you know where to go,' he said, as I followed him inside.

'Yes, I do. Thanks.'

'Sorry to seem suspicious, but you know what it's like.'

'Dead right. You can never be too careful these days.'

He moved off down the hall and I made my way up the stairs, remembering back to that night just three days ago when I'd walked up them the first time. A lot had changed since then.

When I got up to the third floor, I stopped outside her door and listened carefully. The television was on with the volume turned up high. It sounded as though it was switched to the news. I pressed my ear against the door and tried to pick out any other sounds, but couldn't hear anything.

I reached down and tried the handle, but it wouldn't give. The door was locked, so I leaned down and checked the lock itself. It was an easy one. Reaching into my pocket, I pulled a credit card from my wallet and manoeuvred it into the tiny gap between the door and skirting. The lock gave without resistance, and slowly I turned the handle.

I stepped into the hallway and gently eased the door closed behind me, putting the chain across it to delay her if she tried to make a getaway. There were no lights on in the hallway itself but the sitting-room door on my left was open, providing some light. I stopped and listened again.

Making as little noise as possible, I slowly put my head round the sitting-room door.

The room was empty. In the corner, the TV blared as a news reporter in some dusty war-torn location gave a dramatic run-down on whatever conflict it was he was covering. A half-drunk cup of coffee sat on the teak coffee table, and next to it was an ashtray with two butts in it. I waited a moment, then, still hearing no sound from anywhere in the flat, walked inside. I leaned over and dipped my finger in the coffee. It was cool, but not cold. Maybe half an hour old. No more than that.

I retreated back into the hallway. Immediately to my right was the kitchen. The door was half closed but the light was on inside. I pushed it open and had a quick look but, like the sitting room, it too was empty. That only left two rooms, one of which was the bathroom, right opposite me at the end of the hall. Its door was wide open. I crept up, paused for a moment, then reached round and pulled on the light.