'Let's turn it off, Andrea,' he said. 'We can watch it again in a minute.'

She shook her head angrily. 'No. I've got to see. I've got to.'

On the film, Emma pushed her body back into the wall, craning her head away from the blade, her pale blue eyes never leaving it.

Andrea's moaning grew louder. It stopped abruptly when the point touched Emma's neck. Ever so gently.

No one moved a millimetre. It was as if they'd been frozen to the spot, staring hypnotized at the screen. Waiting.

The blade traced a slow path up the contours of Emma's jawline and on to her cheek, brushing the pale skin but not breaking it, stopping at the fold of skin just below her left eye. Half a centimetre more and it would be caressing the eyeball.

Bolt steeled himself for what might be coming next. He prided himself on being a hard man, able to take some of the worst experiences the world had to offer, but this was tearing him up inside, and he wondered how many times this scene would be revisiting his dreams in the coming months.

The knife jerked suddenly to the side, moving like a flash. Disappeared from view.

Emma cried out. Andrea gasped. Bolt stopped breathing.

The camera panned inwards. Emma's face filled the screen. Terrified, but unmarked. Then it panned slowly outwards as Emma crumpled into a fetal position on the bed she'd been sitting on, dropping the newspaper to the floor. She was wearing handcuffs, and there was a chain attached to her ankle by a metal loop.

Something dark rose up from the bottom of the screen, blocking out everything else, and the camera took several seconds to focus on it. It was a piece of paper. Five words were written on it in bold capitals: NO POLICE OR SHE DIES. The camera stayed on it for a full three seconds. Then abruptly the film ended and the screen returned to Andrea's homepage.

For a long moment, no one spoke. Bolt was just about to open his mouth to tell Andrea to be strong, that this was just a method for the kidnappers to cow her into submission so that she'd get them the next tranche of the ransom money – even though he wasn't at all sure he still believed it – when in one ferocious movement Andrea swept the laptop off the table, sending it crashing to the floor, and jumped to her feet. She grabbed the photo of Emma as a toddler from the desk and hugged it to her chest. Pushing Turner out of her way, she swung round to face Bolt, her tearstained face a twisting combination of torment and rage.

'They're going to kill her, aren't they? That's it.

They're going to kill her.'

Bolt put a hand on her arm, trying to calm her. 'No, Andrea, they won't. They're far better off keeping her alive.'

'They told me not to involve the police, and now look at you all here.' She yanked herself free and swept an arm dismissively round the room. 'Standing around while my daughter's tortured by these bastards. Oh God. If they kill her… if they kill her, it's all going to be my fault!'

'You can't think like that, Andrea,' said Bolt, but she was no longer listening. She strode rapidly past them and out the door, leaving behind only grim silence.

Marie went after Andrea, and Bolt heard them both going up the stairs, Andrea shouting at Marie to leave her alone. He stood staring at the upended laptop, wondering how Andrea was ever going to recover from this. Finally he broke his reverie and turned away.

Turner was speaking into the phone. When he hung up a few seconds later, Bolt asked him if they'd got a trace.

'He called from a mobile on a back street in the N18 postcode. But he switched off straight away so we can't follow him.'

'So he knows what we can do with mobile phones.'

'Looks that way, doesn't it?'

'Any chance of getting anything from the email he sent?'

'We won't get much out of the email address itself. Anyone can set up a hotmail account anonymously. But we should be able to locate the computer he sent it from. It might take some time.'

'Get the team on to it straight away. We've just got to hope this guy makes a mistake.'

'He hasn't made any so far.'

Bolt might have liked Turner, but his occasional habit of accentuating the negatives could grate at times. Especially times like this. 'Just do it,' he said, turning away and pulling out his own mobile. 'And get the local cops down the street where the call was made from, just in case he's still there.'

He unlocked the French windows in the living room and went out into the back garden, dialling his boss's number. When Big Barry answered, he explained to him what the kidnappers had done. 'These guys are good, sir. They know exactly which buttons to press. But there's something else too. The way they're tormenting her – this is personal. I'm sure of it. Someone really wants Andrea Devern to suffer.'

'Well, let's hope you're right, because that might help lead us to them. The woman can't have that many enemies. In the meantime, though, I've had authorization for us to set up a sting. Looks like the ladies and gents upstairs agreed with you about negotiation. It's pointless with people as ruthless as this.'

'It's definitely the right move. This way we'll be the ones in control.'

'We'll use bundles of counterfeit notes fitted with trackers.'

'These people are professionals, sir. They're going to spot something like that.'

'We'll be right on their tails. By the time they realize the notes are fake it'll be too late and they'll be in custody.'

Bolt wasn't convinced. 'But it also might be too late for Emma. If they pick up the money, then check the notes in the car, see that they're not real, they'll know we're involved. In that case, they might never lead us to her.'

'Come on, old mate, how am I going to get authorization to use half a million pounds of real money? And where am I going to get it from? The Christmas kitty? Think about it.'

'You said we're not going to lose them.'

'We're not.'

'So we can afford to use the real thing, surely?' Bolt thought of the photo of Emma as a toddler, playing with the hosepipe in her pink swimming costume. 'This is a young girl's life we're talking about.'

'Let's not get sentimental, Mike.'

'I'm not. But if we use fake money and it all goes wrong, it's not going to look good for any of us, is it? That we thought the money was more important than our kidnap victim.' He resisted adding 'heads will roll', but the point was a valid one. Bolt was appealing to Barry's innate arse-covering instincts, knowing that there lay his greatest chance of success.

And it seemed to be working. 'I'll talk to them upstairs, but I can't see them going for it.' Barry sighed. 'Look, this whole operation needs to be well planned, so I want you back here so we can discuss the details. As soon as poss. Keep Turner and the liaison there with Mrs Devern, just in case they make contact again.'

Bolt hung up, and looked at his watch. It was ten past one. His stomach was growling and he realized that he hadn't eaten a thing all day. He'd grab some lunch on the way back. He took a deep breath. One way or another, he was going to get these bastards. And get Emma back for Andrea as well. The hunt was on now, and on the ground at least, he was the one in charge. This was the part of the job he loved, when the battle lines were drawn and it was all about you and them. Pushing the images of the video aside, he felt a renewed sense of determination.

He became aware of a presence behind him. It was Turner, looking vaguely sheepish.

'Everything all right, Matt?'

'Mrs Devern wants a word with you upstairs.

Alone. She doesn't want to talk to Marie.' There was a vague disapproval in his tone.

'OK, thanks.'

Bolt walked back into the house through the French windows. Marie was standing at the bottom of the stairs, looking concerned.