The five-bar took nearly two minutes to open. She was out of practice, and she also had to work hard to keep quiet and calm, knowing that she could be disturbed at any time. Across the corridor she could hear rap music playing and the sound of voices shouting at each other, and she was sweating by the time she finished.

The other two locks were older and less sturdy and took her thirty seconds between them. Then, after a final listen at the door, she opened it and slipped inside, feeling a rush of illicit excitement.

She found herself in a small, sparsely decorated living room. At the far end a door was partly ajar and beyond it she could hear soft snoring. John Gentleman was clearly out for the count. She shut the front door, spotting his landline handset on the mantelpiece next to a photo of a young girl of about five or six in school uniform, smiling at the camera. This would be his granddaughter, Tegan. Tina had done her research on Gentleman. He lived alone, having divorced eight years earlier. The sight of his granddaughter suddenly made her feel guilty, because it brought home to her exactly what she was doing.

Forcing herself to concentrate, she crept across the room and peered round the bedroom door. Gentleman was flat out on his back in a pair of baggy boxer shorts, the covers half off him. Tina glanced round the room, looking for any other handsets, but there weren't any. This was good. It made her task easier.

Retreating into the living room, shutting the door as much as she could, she picked up the handset from the mantelpiece and took the back off it. Then she reached into her jacket and pulled out a thin piece of plastic about three inches long and less than half an inch wide, which she inserted into a space inside. This was a handset tilt switch, a phone-tapping device with a tiny mike and its own power source which would activate automatically as soon as the handset was lifted up and would record every conversation made on it until the battery flattened. Tina had picked it up on the way over here. It wasn't exactly cutting edge, and could be detected easily by someone who knew what he was doing, but she knew Gentleman wouldn't know so it served her purpose well enough.

Having put the handset back together and replaced it on the mantelpiece, she took a pay-as-you-go mobile phone she'd picked up earlier from Carphone Warehouse from the same pocket. She switched it on and attached its hands-free kit before placing it in the corner of the room behind the TV, where it wouldn't be seen. This was her back-up listening device, in case the handset tilt switch didn't function properly. Although only a cheap standard phone, she'd made some alterations to the settings menu on the way over, turning off the ringer tone and setting it to auto answer, which would turn it into an open mike as soon as she called the number and allow her to listen in on anything said in the room. Even now, she was still taken aback by how easy it was to eavesdrop on people. Gentleman would no doubt discover the phone eventually, but by then she would have the information she wanted and there would be no way of tracing it back to her.

She left the flat as quietly as she'd entered it, using the picks to relock the door. Then, keeping her head down to remain as inconspicuous as possible, she walked back to the car. It was only when she was inside with a cigarette in her mouth that she allowed herself a small smile for a job well done.

She pulled out her mobile. It was ten to two, and still no call from Mike. Time, then, to put the plan into action.

She called Rob Fallon. 'Go for it,' she told him, before disconnecting.

Then she switched on the receiver, connecting to the handset tilt switch in Gentleman's phone, put in her earpiece and waited.

I was standing in a phone box on the Edgware Road when I got the call from Tina. As soon as she'd hung up I picked up the receiver, took a deep breath, and dialled John Gentleman's landline number.

It rang for a long time before going to message. I didn't leave one, just counted to five and called again.

This time he answered, sounding groggy and pissed off. 'Who's this?'

I took a deep breath, then spoke clearly and slowly, as Tina had instructed. 'John Gentleman, I know that you're involved in the kidnap of Jenny Brakspear who lives in the apartment building where you work. You provided the kidnappers with a key to get into her apartment, you broke the security camera at the exit to the underground car park so they could get back out, you cleaned up after them-'

'I don't know what you're talking about!' he shouted, but there was uncertainty in his voice.

'You do, and if you admit it to me now and tell me who the kidnappers are, then I'll make sure your name doesn't get mentioned.'

'I told you: I don't know what you're fucking talking about!'

'You know they're going to kill her, don't you? And when they kill her, you're going to be an accessory to murder, and that means years behind bars. And you know exactly what that's like, don't you?'

'Who the fuck are you?'

'The one person who can help you. You've only got one chance to get out of this, Mr Gentleman, and that's to cooperate. Tell the police who you're working for, otherwise I'm going to spend every waking hour for the rest of my life building a case against you, and I'll make sure you go down for murder. Do you understand me?'

'You're that bloke who was with her, aren't you? Well, you listen to me! You can't prove a fucking thing! All right? And you're a dead fucking man messing around in stuff that doesn't concern you!'

'We'll see,' I said, and cut the connection.

Now there was absolutely no way back.

I called Tina. 'It's done.'

'I know,' she said, 'I heard you. Very menacing. Now we'll see what he does.'

It didn't take Gentleman long to react. As Tina listened, he made a call out from the landline, just as she'd hoped. Unfortunately, she had no way of knowing the number he was calling, but that didn't matter. If necessary, she could contact the phone company and find that information out later.

There was no answer at the other end, just an automated voice asking him to leave a message.

'I've just had a call from that bloke who saw you at the flat on Sunday night,' said Gentleman breathlessly into the phone. 'The bastard's threatening to go to the law and turn me in. This whole thing's getting out of fucking hand. You've got to do something because I ain't taking the rap for it. Call me back ASAP, OK? I'm at home.' He reeled out the number. 'I'm getting very worried here, and if I don't hear back from you soon I'm going to go to the law myself!' He slammed the handset back in its cradle, and the tilt switch stopped recording.

Tina exhaled. She'd just heard the final proof that the kidnapping had actually occurred. Now she knew she had to do something. Unfortunately, by illegally tapping Gentleman's phone she'd put herself in a difficult position. If she went with the recording to DCI Knox, or the Kidnap Unit, she was going to have to answer some very inconvenient questions. But if she didn't…If she didn't, it might cost Jenny Brakspear her life.

Tina suddenly felt completely alone. She knew who she needed to speak to. But the one person who'd be able to get her out of this predicament and move things forward without her losing her job was currently off the radar.

'Where the hell are you, Mike?' she whispered, staring out of the windscreen towards Gentleman's apartment block.

She stubbed out her cigarette, took a drink from a bottle of mineral water on the seat next to her, and phoned Bolt for a third time. Once again he didn't pick up. Once again she left a message, except this time she said that the kidnapping had definitely occurred and that she needed his help desperately. She cursed herself afterwards for using that word. It made her feel weak. Yet, if truth be told, she was feeling pretty desperate.