Donna had her arm around his waist. He was slightly shorter than her, with fair, spiky hair.

Then there's one here for the Christmas ball in our first year.'

In the official photograph there were several unidentified men, none of whom were standing beside Donna. But in two of the shots by students, Donna was with a taller man. One was slightly out of focus, but the other was clear and showed a man with facial features similar to their photofit.

Where is he in the group shot?' asked Sophie.

It's not clear,' she replied. But there's someone behind the woman on the far right, mostly obscured by her head. There's a later group shot, taken after the meal. There's someone behind Donna, again almost hidden. We wonder if that's someone's hand on her left shoulder.'

It would be great if we could take these, and the digital image files. We can get them back to their owners if necessary.'

We're pretty sure they're all copies, so there isn't any need. I think we're all glad to be of some help.'

The two detectives had a coffee with David Bell and then left.

What do you think, Jimmy?' Sophie asked as they walked to the car park.

It looks like him, ma'am. He doesn't appear in anything before that Christmas ball, so I wonder if he met her there. But he doesn't seem to be a student.'

The early shots of that evening show her with groups of friends, and not with any particular man, so I'd guess the same as you. Either that or he was her boyfriend already and arrived later than her.'

But if he didn't know her, and he wasn't a student, how did he get a ticket?'

It's not that difficult, Jimmy. There are all kinds of ways of blagging entry to a student function. I used to do it regularly in my younger days. I once talked my way into a formal student ball at the university in Bristol when I was only sixteen and still at school.'

Melsom was quiet. He glanced sideways at his superior.

We need to get some of the team to go through these photos carefully. There might be a chance that one of the shots shows him earlier on. If he's on his own then that should settle it. I think we'll work on the assumption that he met her there. I think we should try to trace her first boyfriend, George Warrander. He might be able to confirm some of our suspicions. Can you do that, Jimmy?' She paused as they reached her car. Are you okay, Jimmy?'

Oh, yes, ma'am . . .' But he looked uneasy.

Are you sure?'

I've been thinking about the knife, ma'am. The one used to kill Donna.'

Yes. And?'

Well, he wouldn't want to get rid of it close to the scene, would he? It would be found by our search teams too easily. And it might have something on it that might link it to him.' He paused again.

Jimmy, are you doing these pauses for dramatic effect?'

No, ma'am. I'm just getting my thoughts in order. We wouldn't expect a killer to hang on to the knife, would we? If we did trace him in the end, we'd find it and that would be really strong evidence against whoever it was, wouldn't it, especially if it could be shown to be the one used? So he'd want to get rid of it pretty quick, but not somewhere it might be easily spotted. So he'd choose somewhere miles away, like a rubbish skip, and wrap it up well. But the thing is, if he was trying to frame Berzins, wouldn't he want the knife to be found, so isn't it likely that he left it somewhere we'd find it? He went from here to Corfe, to Donna's mum's cottage. What if he cleaned it up a bit, and put it into her kitchen? It wouldn't look out of place there, would it? But he might expect us to check for it. And if it's not there, it could be in Susie's flat.' He thought for a few moments. It would be better at Susie's, from his angle. It would make the link between the other two murders and Susie's stronger.'

Jimmy, you're a star. You're thinking like a detective. We'll do the Bournemouth end now, since we're here, then check on the cottage on our way back. I can remember seeing some knives in the kitchen drawer in Susie's working flat. We're looking for a heavy-duty kitchen knife with a fifteen centimetre blade, if I remember correctly. That's about six inches. I'll phone Kevin McGreedie.'

They were told that a knife of the correct dimensions had been found in the kitchen of Susie's working flat. It was waiting its turn for forensic examination, so Sophie asked for it to be examined next as a priority. She also discussed the plans for calling the mobile number associated with the Andy listed in Susie's contacts. She decided to make another attempt that afternoon.

If you're right, Jimmy, then the knife will have traces of Donna's blood on it. Deliberately left to implicate Berzins. But is our killer aware of just how small the samples need to be in modern forensics? There might also be something that can be used to identify him. We can but hope. I'm going to call into Poole on the way back to check that Tracy is okay. She phoned me yesterday evening to say she was settled in, but I still want to make sure. But first to the Bournemouth nick. We have a phone call to make.'

CHAPTER 16: Shock.

Monday Afternoon, Week 2 A call-tracing system had been set up in the Bournemouth incident room to track the signal if the phone was answered. Sophie was to make the call, since a woman's voice might not arouse as much suspicion as a man's.

She waited as it rang. It was finally answered by a gruff voice saying, Yeah?'

Andy?'

Who is it?'

The police team had discussed what persona Sophie should adopt. After much debate, they had decided that to use a real name from Susie's contact list might be too risky. The same applied to the women identified on the assault list, such as Tracy Beck or Sasha Purfleet.

It's Ella.'

There was moment or two of silence.

Who?'

Ella. I'm a friend of Susie's,' Sophie added.

There was another pause. Then came a verbal torrent that made the listening police team sit up.

Oh no, you're fucking not. I know who you are, you slutty cow. Prancing around in your posh silver car with your posh law degree and your posh education. I bet you've got them all twisted around your finger, haven't you? Dancing around when you click your fingers. Yes ma'am, no ma'am, three fucking bags full, ma'am. Well, you can just fuck off and screw yourself. I bet you've got call-tracing on, haven't you? Well you're gonna be shitting yourself in a couple of minutes. I mean, really shitting yourself. I'm laughing. I'm nearly pissing myself imagining the look on your face, you skinny bitch. You can just fuck off and die, and when you do I'll come and piss on your grave.'

He hung up.

The detectives stood in silence for a few seconds before turning to the technicians operating the tracing equipment. They looked grim.

Our kit here showed somewhere near the riverside in Wareham, but nothing more precise. The call was just a bit too short. But we've got a link with the service provider. Tom here was on the phone to them as you spoke to him.'

The second technician finished his conversation. Sophie held her breath.

We've got him located in a residential area north east of Wareham quay, but it's not exact. The signal was centred on a road called Spider Lane.'

Sophie's face went white. That's where I live! He's at my house, and Hannah's there alone. Get a squad car there now!'

As she ran down the corridor towards the car park, Sophie phoned home on her mobile, praying that her daughter would answer.

Hi, Mum,' came Hannah's calm voice.

When Sophie, Melsom and Kevin McGreedie screeched to a halt outside the Allens' cottage in Wareham, a squad car was outside with its blue light flashing. Sophie ran to the door and found her daughter in the hallway, in conversation with two uniformed policemen. She threw her arms around Hannah and hugged her so tight that she struggled for breath.

What's this all about, Mum?'

Was there someone here, sweetheart?' gasped Sophie. Are you sure there were no callers?'

No, though I was out for a while to take some stuff to the post office. I got back, let myself in and then you phoned. About ten minutes later the police car arrived, with its siren going. If you hadn't been on the phone to me at the time I wouldn't have known what was going on. These two charming officers aren't totally clear either. I've just made a pot of tea for us. Want some?'

McGreedie had just entered the house. Sounds like a good idea. I think we all need a cup,' he said.

He took charge. He spoke to the officers from the squad car and asked whether they'd seen anything suspicious as they approached the house. They had noticed nothing unusual.

Jimmy Melsom seemed to have disappeared. Sophie was just about to send one of the PCs out to find him, when he walked into the lounge. He whispered into McGreedie's ear, but shook his head when Sophie looked at him.

Later,' he mouthed.

When's your train, Hannah?' Sophie asked.

About half an hour. I was just getting my bag together when the police car arrived.' She looked at the clock. I'm going to have to go.'

I'll take you. I need to take Kevin back to Bournemouth, so I'll drop you at the station on the way.'

No need to take me all the way back, Sophie,' said McGreedie. I'll get the train with Hannah. That way we can be sure she's on her way safely, and you don't need to waste any time. I'll get a car across to pick me up from Bournemouth station and she can travel on to London.'

Kevin, I'm so grateful.'

Sophie's face was tense, exhausted.

They dropped Hannah and McGreedie at the railway station. Then Melsom told Sophie what he'd been doing when she rushed into her house.

I had a look around but couldn't see anything odd, just like the two car-cops. But then I saw a curtain twitching in a house two along from yours, so I called in.'

Mrs Bentley? An elderly lady with a walking stick?'

That's the one. Anyway, she'd spotted a white van sitting opposite her own neighbour's a bit earlier. That'll be three away from you. It was on the other side of the road. She reckons the driver was watching the road. He wasn't doing anything, just looking. But then she saw him take something out of his pocket and hold it up. She thinks it was a camera. And when she looked along the street, Hannah was just arriving at your front gate. Then he took out what looked like a phone and held it up to his ear. I asked if he seemed to dial any numbers, but she didn't think so, although she can't be sure. He stayed another few minutes, just watching again. What made her remember it all was that he left just before the police car arrived. She reckoned he started the engine just after she heard the siren. It was that made her suspicious. It's a shame she didn't get the registration.'

Do the times match? The phone calls, I mean? Ours and this man in the van?'

Melsom nodded. I think so, ma'am, as far as I can tell. That's what I told the DI when I first came in. He's going to put out an alert for the van, even though we don't know the registration.'

Christ. How did he find out where I live? And why was he watching the house? Did you show her the photo?'

Yes. She couldn't be sure, but she said it looked like him.'

God, Jimmy. I just don't know what to make of this. It looks like it was almost certainly the man I called. But why was he there? What could he have been up to?'

It's a game, ma'am.'

What?'

He's treating it as a game. He's found out you're in charge, so you're now his opponent.'

So while clever little me has been thinking that I'm one step ahead of him because everyone thinks we've got Berzins as the killer, the reality is that he's done a neat side-step and is probably one step ahead of me. But how did he find out my address?'

Probably from the web. If he knew your name it wouldn't be hard. You'll be on the voters' roll. But he isn't really one step ahead of us, ma'am. It doesn't alter the investigation, does it? And surely he'd have been better off just putting the phone down rather than giving you all that spite. It shows us what he's like, doesn't it?'

And we now know a bit more about how he operates, which we wouldn't have done if we hadn't made the phone call. He'd have started collecting information on me and my family, and we wouldn't have known.' Sophie paused. He may already have stuff. My God. Maybe he already knows about Jade.'

Who's Jade, ma'am?'

My younger daughter. She's only fifteen.'

She glanced at her watch. Three twenty. Sophie stopped the car and began making calls. The first was to the head of Jade's school, asking her to keep the girl on site and under supervision until collected. The second was to the Dorchester school where Martin was head of the maths department, asking for an urgent message to be sent to him. She then swapped places with Melsom, asking him to drive the rest of the way to Poole so that she was free to handle phone calls. Her husband called back quickly. She explained that Jade might be in danger. She would remain at school until collected by Martin.

I can't collect her myself, Martin. I'm up to my eyeballs in this thing. Can you do it? Okay, love you.'

Sophie looked at the silent phone for several minutes before putting it back in her bag.

The hotel in which Tracy Beck, her daughter and partner were staying was several streets away from the quayside in a tourist area of the town. They found Tracy and Rachel in the small secluded garden.

I want you to stay in the hotel, Tracy. This garden is fine, it can't be seen from the street. But please don't go out.'

But what about Rachel? I don't want her to miss more than a day or two off school. And if she is here all day she'll get bored. I took her to the quayside for a walk this morning, and she loved it.'

Not a good idea. Find someone else to take her if she needs to go out, but I don't want you outside these walls. It's just too dangerous for you. Look, let me be more explicit. If he finds you, there's a chance that he might try to kill you. We think he's already murdered a young woman, which is why we're looking for him. I've decided to allocate an officer to stay with you for the present. She'll be down later today.'

What good will that do if he's turned as violent as you say? He's really strong, believe me.'

We know that. Don't worry, she'll be able to handle it. But try to keep Rachel inside as much as possible. Hopefully this will all be over in a couple of days. And trust me, Tracy. It'll be fine as long as you do what I say.'

When they got back to Swanage they found that Marsh had managed to interview the owners of the flat above Donna's. The couple had heard several bumps as they'd passed by Donna's door on the previous Monday evening. They confirmed the time at mid-evening, when Donna and Berzins were both at work.

That's good. Now we need a statement from the residents who saw someone leaving Donna's building mid-evening. Is that coming, Barry?'

Marsh hadn't been able to contact them at the weekend. They'd been away at a family wedding, but were due to return the following day. He and Pillay had made some progress in tracing one of the other assaults, on Sasha Purfleet from Bournemouth. The name hadn't shown up on any of the police databases, but the hospital had treated her for a leg injury in 2006. The record gave an address but no telephone number, so Lydia had gone to check on the lead.

What did you discover in Southampton, Barry?'

Debbie Martinez started assault proceedings in January 2005, but dropped charges within a week. I spoke to the officer in charge, Gwen Davis. She was a DC then, but she's a sergeant now. I like her. She seems a thorough and genuine sort, so I trusted what she said. Apparently Debbie dropped the charges because she just couldn't face the thought of a court appearance, and because she didn't believe that her injuries were serious enough. Gwen tried to talk her into continuing, but it was no use.'

And she remembers the man? Andrew Renshaw?'

Yes, although her memory's a bit vague. It was six years ago. She just confirmed that he was tall and heavily built, though not fat. He looked as if he kept himself fit.'

Did she remember anything about his character?'