She was about to come up with some other smart-alec answer but we were interrupted before she could get it out.

'Can I help you, gentlemen?'

The speaker was an attractive white female, early forties. Quite tall – about five feet nine – and, from the sound of her voice, someone in authority.

I turned in her direction and smiled, opening fire with the charm. 'I hope so. My name's DS Milne and this is my colleague, DC Malik. We're here as part of an ongoing inquiry.'

She managed a weak smile. 'Really, what now?'

'It's a murder investigation.'

'Oh.' She looked taken aback. 'Was there any reason why you were talking to the children?'

'I was just introducing myself.'

'No you weren't,' said the girl. 'He was trying to find out who we were.'

'Well, I'll take over from here, Anne. Aren't you and John meant to be with Amelia?'

'We're just having a quick smoke,' said the girl, not bothering to look up.

'Perhaps you'd better come inside, gentlemen, and we'll talk in there.'

I nodded. 'Of course. And you are?'

'Carla Graham. I manage Coleman House.'

'Well, then, please lead the way,' I said, and we followed her through the double doors and into the building.

The place had the unwelcoming feel of a hospital: high ceilings; linoleum floors; health-related posters on the walls warning against shared needles, unwanted pregnancy, and a whole host of other obstacles to a happy and fulfilling life. And there was a nasty reek of disinfectant in the air. Dr Barnardo's this wasn't.

Carla Graham had a spacious office at the other end of the building. She ushered us in and we took seats facing her across her sizeable desk. There were more doom-mongering posters in here as well. One showed a huge photograph of a young child, no more than five, covered in bruises. The caption above it read: Stamp on Child Abuse. Below the photograph it added: Not on Children.

'So, what's happened?' Carla asked. 'I hope none of our clients are involved.'

'Clients, meaning children?' It was Malik asking the question.

'That's right.'

'We don't really know, which is why we're here.' I then told her about the discovery of the body the previous day.

'I didn't hear anything about that,' she said. 'Who was the poor girl?'

'Her name was Miriam Fox.' Carla's expression didn't hint at recognition, so I continued. 'She was an eighteen-year-old prostitute, a runaway.'

She shook her head and sighed. 'What a waste. Not a shock, because the potential for this sort of thing to happen's there all the time. But a terrible waste, all the same.'

Malik leaned forward in his seat and I immediately got the feeling that he didn't much like Carla Graham. 'I assume you didn't know her?'

'I don't know the name, no.'

I took the photo of Miriam posing for the camera out of my suit pocket and passed it over to her. 'This is her. We think it's a recent picture.'

She studied it for a long moment before handing it back to me. As I took it back I noticed she had graceful hands with well-kept, unvarnished nails.

'She looks vaguely familiar. I may have seen her before with one of the clients, but I couldn't say for sure.'

'We've been talking to some of the other girls who work the same area as Miriam did and they say she was particularly friendly with a girl called Molly Hagger. They said that Molly lived here at Coleman House.'

'Lived is the right word. Molly was a client of ours for some months but she walked out about three weeks ago now and we haven't seen her since.'

'You don't seem too worried about that, Ms Graham,' Malik said, only just about concealing his dismay that she should take the loss of one of her 'clients' so lightly.

'Mr Malik,' she said, turning towards him, 'Coleman House is home to twenty-one children aged between twelve and sixteen, all of whom come from disadvantaged backgrounds and all of whom have behavioural problems of varying degrees of seriousness. They are placed here by the council and we try to do our best for them, but the law is not on our side. If they want to go out at night, they go out. If I or any of my staff lay a hand on them to try to stop them leaving, they can have assault charges laid against us just like that, and believe me they'd do it. Put bluntly, these kids do what they like because they know they can do what they like. Half of them can't write their names, but they all know their rights inside out. And often, I'm afraid, they simply decide they've had enough of us and walk out the door. Sometimes they come back; sometimes they don't.'

'Don't you try to look for them?' Malik persisted.

She looked at him in the way a teacher looks at a particularly foolish pupil. 'We're extremely understaffed. It's hard enough keeping control of the ones who want to be here without worrying about the ones who don't. And where would we look for her? She could be anywhere.'

'Did you report her missing?' I asked.

'I informed Camden Social Services and they will have informed the police, but I didn't report it myself. I didn't see much point.'

'How old is Molly Hagger?'

'Thirteen.'

I shook my head. 'It's a young age to be out on the streets.' It was. Far too young.

She turned to me now. 'Mr…?'

'Milne.'

'Mr Milne, I can understand if you think I'm not taking Molly's leaving seriously enough, I can understand both of your concerns, but try to look at it from my point of view. I've been a careworker for a long time now, and I've tried to help a lot of kids make a better life for themselves. But the older I get, the harder it becomes. You see, a lot of the time these kids don't want to be helped. They get plenty of offers, I can promise you, but most of them just want to live fast, take drugs, drink. They're independent, but independent in all the wrong ways. They can't stand any form of authority but often they aren't capable of looking after themselves. They're not all like that of course, some do actually want to listen and learn, and they're the ones I find myself gravitating towards. But if I've tried to help someone, and they keep turning their noses up at that help, then eventually I have to stop.'

'And was Molly Hagger like that? Was she one of the ones who turned her nose up?'

'Molly came from a very difficult background. She was sexually abused from the age of four by both her mother and her mother's boyfriend. She was taken into care at the age of eight and she's been in it ever since.'

I thought of the girl in the photograph and felt mildly sick. 'Jesus…'

'It's far more common than most people think. You should know that, Mr Milne.'

'It doesn't make it any easier.'

'No, you're right, it doesn't. But, to answer your question, Molly wasn't one of our more difficult girls. She didn't resent her carers in the way some clients do, but she had a very different outlook on life that was a direct result of the experiences she'd suffered.'

'What do you mean?'

'Well, she had a very casual and very adult view of sex. She had male and female sexual partners from a very young age, and from the age of ten she was charging for her services to certain individuals.'

'Has she run away before?'

'She's walked out on a number of occasions and not been seen for some time. The last time of any significance was about a year ago when she took up with an older man. She ended up living with him for several months before he got tired of her and threw her out. That's when she came back here.'

'So you think that might have happened this time?'

'I would think, knowing Molly, that that's a very likely scenario.'

I nodded, more optimistic now that she was still alive. 'We're going to need to speak to all your other, er, clients, and the rest of the staff to see if anyone else knew Miriam Fox and might be able to give us any relevant information.'