I continued smoking the cigarette until it was down to the butt, then I used it to light another one. When that one was halfway down, I knew I could hold back no longer. The thing is, I can never sit still when there's a new investigation starting, particularly a murder. I get a kick out of catching killers – maybe for the wrong reasons, I don't know, but it makes me feel good letting them know it's me who put them down, fucked up their whole lives.

And, if nothing else, getting involved in this one would at least stop me mulling over matters I could do nothing about.

So I stubbed out the cigarette in the already overflowing ashtray and headed down to Regent's Canal, the grimy scene of many a heinous crime.

It was twenty to ten and raining when I arrived at the murder site. A uniformed officer stood at the entrance to the towpath talking to a guy in a trench-coat who looked like a journalist. It's amazing how quick these people sniff out a story; it's like they've got an extra sense that can detect a fresh kill from miles away. I pushed my way past the journo, who gave me a dirty look but thought better of saying anything, and nodded to the uniform. I recognized him from the station, although I couldn't put a name to him, and he evidently recognized me because he stepped aside and let me through.

This part of the canal was fairly well looked after. The old warehouses had been knocked down to be replaced by office blocks that were built a few yards further back from the water's edge. A well-trimmed lawn had been laid down in the extra space with a couple of benches to add to the park-like feel.

The painstaking, monotonous hunt for clues was already in full flow. There were about two dozen people widely scattered across the scene as they picked, probed and photographed every patch of earth. At the canal's edge stood four police divers, fully kitted up, ready to enter the treacle-like water. One of them was talking to DCI Knox, my boss's boss. He would be the senior investigating officer on a case like this, responsible for making sure that the investigation ran smoothly and nothing was missed. Almost certainly the key to a conviction lay in these few square yards.

A tent had been erected at the entrance to a narrow gap between two of the buildings. This was where the body would be and where it would remain until it had been examined and photographed in minute detail. I could see my boss standing next to the tent, talking to one of the forensic team. I made my way over, nodding to two CID men I recognized: Hunsdon and Smith. They were standing by one of the benches taking a statement from an old guy who had a Jack Russell on a lead. I guessed the old guy had discovered the body. His face was pale and troubled, and he kept shaking his head, as if he couldn't believe what he'd seen, which he probably couldn't. It's always difficult for people when they come into contact with the handiwork of murderers for the first time.

My boss turned round and nodded a curt greeting as I approached. It was a cold day, but DI Karl Welland was sweating. I thought he didn't look well. This was nothing new. He was overweight, red in the face, highly stressed, and, if my memory served me right, the wrong side of fifty. Hardly a candidate for a ripe old age. He looked worse today than usual, though, and his pale skin was covered in vivid red blotches. I felt like telling him he needed a holiday, but I didn't. It's not my business to offer lifestyle advice to my superiors.

He excused himself from the conversation he was having and led me into the tent. 'It never gets easier, you know,' he said.

'The dead'll always keep dying, sir,' I told him.

'Perhaps, but do they have to die like this?'

I stopped and looked where he was facing. The girl couldn't have been more than eighteen. She was lying on her back in the paved alleyway between the two buildings, legs and arms splayed open in a rough star shape. Her throat had been cut so deeply that the wound had come close to severing her head, which was tilted at an odd angle to the rest of her; thick dried blood had splattered across her face and formed in irregular pools on either side of the body. Her black cocktail dress had been ripped badly around the chest area, exposing a small pointed breast. It had also been pulled up round her waist. She hadn't been wearing any underwear, or, if she had, she wasn't any longer. There was also a lot of congealed blood around the vaginal area, suggesting that her killer had stabbed her there as well, although I thought immediately that this would have been done after death as there didn't appear to be any defensive wounds on her hands or lower arms. She had died quite quickly, I was sure of that. Her face was screwed up in pain and her dark eyes bulged out, but there was no fear in them. Surprise maybe, shock even, but no fear. She was still wearing one of her shoes, a black stiletto. The other lay on its side a few feet away.

'She must have been freezing dressed like that,' I said, noting that she wasn't wearing any stockings or tights, nor were there any in the vicinity of the body.

'Looks that way,' said Welland. 'She was partially covered with an old rug when we found her. It's already gone off to the lab.'

'What do we know so far?' I asked, still looking down at the corpse.

'Not a lot. She was found just before eight o'clock this morning by a bloke walking his dog. There hasn't been a great deal of effort to conceal her, and it doesn't look like she's been here that long.'

'I'd say by the way she was dressed, she was a tom.'

'I think that's probably a fair assumption.'

'Goes off with a punter to a nice secluded spot, he pulls the knife out, puts a hand over her mouth, and the rest is history.'

'Looks that way, but we can't tell for sure. A lot of girls go out scantily clad these days. Even in weather like this. The first thing we need to do is identify her. You're on the squad for this one, Dennis. DC Malik'll be working alongside you, and you'll be reporting to me. DCI Knox is the SIO.'

'I've got a lot on at the moment, sir.'

'You're going to have a busy week, then. I'm sorry, Dennis, but we're short on bodies, if you'll excuse the pun. Very short. And it seems the world's lowlifes are all busy at the moment. What can I do?'

What could he do? He was right, of course. We were snowed under, and in those circumstances it's a case of all hands to the pumps. I was already losing my initial enthusiasm, though. It just didn't look at first glance like it was going to be an easy case. If this girl was a prostitute, it was highly likely we had a sex killer on our hands. If he'd been a clever boy and had worn gloves and avoided leaving any liquid evidence at the scene of the crime, then finding him was going to be an uphill battle. Whichever way you looked at it there was going to be a lot of legwork.

I looked back at the pathetic corpse of the girl. Some mother's daughter. It was a lonely way to say your goodbyes to the world.

'I want to get this one solved, Dennis. Whoever did this…' He paused momentarily, choosing his words. 'Whoever did this is a fucking animal, and I want him in a cage where he belongs.'

'I'll get on to it,' I told Welland.

He nodded, wiping his brow again. 'You do that.'