When it came, it caught them all by surprise. Such a stupid way to be caught out, but with not a whisper from David since his meeting with Kate in the cafe they had assumed that he was too busy with the deal in hand to be any kind of real threat to Kate.

They had run out of milk for tea. Kate had offered to go and buy some, but both boys had looked at her in horror. Still not allowed out without a chaperone then, thought Kate.

'There's some in my fridge,' John said, trying to unravel a particularly complicated folder of documents. 'Why don't you go and get it from there, save one of us having to go to the shops?'

'Fine,' Kate said, catching the keys as he threw them to her. Usually they left the doors to the two flats open, but they were all taking extra care at the moment.

Five minutes later, John and Sherlock both realised at the same time that she was taking an awfully long time to get a pint of milk. Looking at each other for a split second, they both raced to the door of 221B and down the stairs. John's door was still shut, his keys lying in the hallway where they had fallen, the street door was wide open.

'Phone Lestrade,' Sherlock shouted as he sprinted out of the door and down the street. A dark blue Bentley was taking the corner of the road way too fast, and he ran after it as fast as he could. He saw it pull onto the main road, and then it was gone.

Shouting in frustration, he turned and raced back to the flat, pulling out his mobile phone as he went. 'I know that he's on the phone,' he shouted to the officer from Lestrade's team who answered the phone. But I need you to get him to track a car numberplate, immediately. Dark blue Bentley, 2007 model, and he gave the officer the number plate of the car which he knew had Kate in it.'

Back at 221B, John was still talking to Lestrade, Sherlock took the phone from him. 'Lestrade they've got her in the car with the number plate your officer is just showing to you. Get it traced, find the car and you'll find the person who's got her. Better still, we can track Kate, hang on. Logging on to Kate's mobile phone account through her computer he tried to track her phone. Depressingly it came up as Baker Street. When phoned it could be heard ringing from the side in the kitchen where she had left it to charge.

'Car is registered to a Xi Ling Chang, Lestrade was saying, a known associate of one of the Chinese Drug Barons that work out of China town, but one we've never been able to pin anything to until now. Doesn't help us track it down, though.'

'Give me five minutes, I'll phone you back,' Sherlock said, fingers poised over the laptop keys.

'What are you doing?' John asked, amazed at how calm Sherlock was being.

'Tracking Kate,' Sherlock said. 'But as its not entirely legal, I think that we should probably made our own way there before we call in the troops.'

'But her mobile phone's here,' John said, confused. 'How on earth are you going to do that?'

Sherlock grinned. 'You remember that watch I gave her for her birthday?

'Its got a tracker in it? You are unbelievable. Does Kate know about this?'

'She didn't ask.'

'And you chose not to tell her.' John was exasperated despite everything. 'I can't believe that you effectively chipped your girlfriend without her knowledge.'

'For her own safety John!' Sherlock shouted. 'Don't you see? I was only ever going to use it in circumstances like this, but unfortunately it is still strictly speaking illegal.'

'So how does it work? Website?'

'Exactly. You log in, then it uses GPS to locate the chip, and hopefully Kate.'

'So what are we waiting for?' John asked, as the map lit up with a moving cursor showing Kate's location. Still in the car then.

Sherlock needed no further encouragement. Grabbing the keys to the land rover from the kitchen drawer he sprinted out of the door, John hot on this heels, laptop in hand.

...

Five minutes later and they were speeding towards the now stationary cursor on the map in the land rover. 'Warehouse,' Sherlock said, 'Of course. Somewhere nice and secluded.'

'Do you want to phone Lestrade?'

'No, not yet, I want to see how the land lies first. Storming in there with a whole load of blue lights might be exactly the right way to get her killed.' His jaw tightened at the thought, and John wisely chose to remain silent.

'Did you bring the gun?' he asked suddenly, aware that Kate's kidnappers were likely to be armed.

'Of course.' Sherlock opened his suit jacket to show John the Browning pistol in the inside pocket.

Arriving at the industrial estates, Sherlock parked the land rover on a patch of waste ground some distance from the warehouse and he and John took a back route towards the warehouse where Kate was being held. Climbing over a final fence, they dropped into the back of the empty car park.

'Now what?' John asked.

'Now we take out the guard,' Sherlock said quietly, 'No, hang on, wait.'

A low black sports car was coming screeching into the car park. Sherlock and John quickly hit themselves behind a group of skips in the corner, just as David got out of the car and sauntered into he building.

'Bastard,' muttered Sherlock, watching him chat to the guard on the door before walking in.

Taking advantage of the guards distraction by David, they waited only a few seconds after the door had shut behind David before John approached the guard with the pretence of asking directions, and Sherlock clocked him on the head with the butt of the revolver. It was elegantly done, and soon they were dragging his unconscious form behind the skips.

'Anyone would think that we'd done that before,' John said. 'Do we phone Lestrade now?'

'If you like, but tell him not to come in all guns blazing. This chap has a gun,' he indicated the unconscious man on the ground,' and I'll bet the others do too.'

Removing the man's pistol he threw it to John, who put it in his pocket. The man also had handcuffs, which were a handy way of ensuring he wouldn't stray too far from the fence, even if he did wake up.

'So how do we find Kate?' John asked. Sherlock showed him his mobile phone, now on the tracking website and showing them distance to 'target.' 'This should pinpoint her to a few feet,' he told John.

'That is a serious piece of kit,' John said.

'Because I'm very serious about keeping her safe,' Sherlock told her with no hint of sarcasm for once. Right, according to this, she must be behind this wall.'

Eying up the corrugated metal wall, he threw his coat to John, and using hand and foot holds made out of pegs, somehow managed to climb the wall like a spider to reach a ventilation window halfway up. Looking in, he gave John a thumbs up. Kate was inside.

When Kate heard Sherlock's voice coming from above her she thought that she must be hallucinating.

'Kate, don't say anything,' his voice said. 'I'm at the ventilation opening about seven feet above your head. Is there a guard there?'

'Yes,' Kate murmured, but he's at the far end of the warehouse. David's just arrived.'

'We saw.' Sherlock said. 'Are you okay, did they hurt you?'

'No, I'm fine. My hands are handcuffed behind me, though, and my legs are tied to the chair.'

'I'm going to drop a lock-picking wire down to you. Can you get your hands against the wall?'

'Yes, give me a minute.'

Kate shuffled her chair back so her cupped hands were touching the wall. Sherlock dropped a wire down to her. The first one glanced off her waiting hands, the second one she caught.

'Now remember your lock picking lessons?' At the time Kate had thought that he was mad. It was part of the 'survival course' that he and John had put her through when they had first got together. As well as combat training and shooting there had been a healthy dose of lock-picking, breaking and entering and various other skills which meant that Kate could have a great second career in burglary should she ever feel that medicine was no longer the career for her.

Kate carefully used the wire to pick the lock of the handcuffs. Fortunately David was still talking to the guard. Eventually she heard the snap as the lock clicked open. 'Good girl,' murmured Sherlock who had heard it too. Now take the cuffs off and drop them to the floor, but keep your hands behind you. I'm dropping you a gun, don't drop it whatever you do. Cup your hands behind you again, don't move them and I guarantee you'll catch it. Kate did so and a few seconds later had the gun in her hands.

'I don't want to use this, she said.

'And I'm hoping you won't have to. Reasonable force, remember? If he threatens you Kate, use it. The police are on the way, but I don't want it to turn into a hostage situation and the guards have got guns.

'Okay. Looks like he's finishing his conversation.'

David looked different. Harder, angrier. Kate felt her pulse begin to race despite her best efforts. 'Hello Kate,' he said. 'I'm sorry that it had to be like this, but I didn't think that controlling boyfriend of yours would talk to me any other way.'

'You could have just asked,' Kate said calmly.

'There's a restraining order, remember? Besides, I thought that you would be more likely to see things my way if we did it like this.'

There was a glint of metal and Kate realised with horror that he had a knife in his hands. He was playing with it carelessly, flicking it back and forth between his fingers.

'The thing is, Kate,' he said slowly, 'your boyfriend is turning up some very difficult information about me and some on my more powerful friends. Information that I would like to disappear. So here is how its going to work. You are going to ask your boyfriend to destroy the information that he has on me, and he will get you back in one piece - eventually. Once our deal is done and I am out of the country. If he doesn't comply, then I'm afraid that I can't guarantee your safety.'

For once in her life, Kate was rendered entirely silent. 'You're very quiet, Kate,' he said, still playing with the knife. Kate saw something in his eyes that she had forgotten. The look that he had before he used to hit her. She had forgotten. He got a kick out of this. He got a kick out of her fear, and out of feeling in control, but there was something more. There was a madness there that she hadn't seen before.

Trying to keep calm, she said, 'What do you want me to do?'

'I want you to phone your boyfriend and tell him to stop digging, and not to involve the police. I want his computer and whatever other information that he has on me before the end of the day or I will send you back to him in pieces.'

Kate felt the cold, reassuring metal of the gun in her hands, and realised that it might be her only chance. David was coming closer to her now, menace in his eyes, gently he stroked the side of her face with the knife blade, flat side down so it wouldn't cut, enjoying her fear. 'But the only question is, Kate, does he love you enough to surrender the game, because from what I've heard of him, I'm not sure that he can bear to lose.' He turned the blade slightly, so it caught Kate's cheek. She felt blood trickling down, she knew that it was likely to be little more than a scratch, but it was a taster of things to come.

There was a ringing coming from David's pocket, distracted he took away the blade and walked away to answer it. 'Yes,' came Sherlock's voice, 'I do love her enough to lose the game, but fortunately enough I won't have to.'

David turned back to find Kate pointing a Browning pistol at him with both hands. He raised an eyebrow. 'Impressive,' he said, 'I didn't realise that you'd become one of Charlie's Angels, Kate.'

'Tell the guard to drop the gun,' Kate said calmly, 'or I will shoot you, David, don't think that I won't.'

David chuckled. 'Very well. Drop the gun,' he shouted to the guard, who obliged. He stood, knife still in one hand, trying to outstare Kate.

'You won't shoot me, Kate, you don't have it in you.'

'I've changed,' Kate said, amazed at her own calm, 'and I swear if you come another inch closer to me David, I will shoot you.'

'No you won't,' David said confidently. 'Come on Kate, give me the gun.'

He made the mistake of taking a step towards her. Kate made a split second decision. John had told her two shots to the chest and one to the head was the traditional way of taking someone out, or was it three to the chest? She had the gun trained on David's chest, but he was right, she couldn't do that. Intent on stopping his progress toward her, she swung the gun down, aiming for the top of his leg and fired. David stared at her in shock as his leg buckled and he fell to the floor, screaming in pain.

'You bitch, you shot me.'

'I did say I would,' Kate said calmly, 'but then you never did take me seriously,'

The guard was warily reaching down for his gun. 'I don't think so, do you?' Kate said, swinging the gun round to him. 'I'm a pretty good shot, you know and I still have five bullets left. I'm fairly sure I could hit you from here. Now why don't you open the door for my friends?'

The guard did as he was told, and seconds later, Sherlock and John came running into the room, John training his gun on the guard until he lay down on the floor as he was told to, and Sherlock coming to untie Kate, who now had the pistol trained back on David.

'You okay?' he asked.

'Fine, thanks,' she said, surprised that she actually was. 'That felt good. Is that wrong?'

He grinned at her. 'Welcome to my world,' he said, not for the first time, 'I always knew you were an adrenaline junkie. Now give me the gun,' he said when he had untied her. She surrendered it gratefully and he trained it on David. 'Police are on their way, now we just have to sit tight.'

Kate stood up, moving as far away from David as she could, and then sat down abruptly against the wall as her legs gave way.

'Kate?'

'I'm fine,' she said, 'Just concentrate on keeping an eye on that bastard.' There was a growing pool of blood on the floor spreading out from the top of David's leg. Kate knew that she should probably put some pressure on it, but she was past caring. He caught her eye. 'Don't even think about saying it,' she spat at him, 'my hippocratic oath is long gone.'

There was the sound of footsteps outside and six members of armed police ran in through the open door. John and Sherlock dropped their guns gratefully as they swiftly handcuffed the guard, and an officer gave first aid to David, while an ambulance was summoned.

Finally Sherlock was able to come and sit on the warehouse floor next to Kate and give her the hug she so badly needed. 'I'm okay,' she said, trying not to cry.

'No, you're amazing,' he murmured.

Lestrade walked in, as the guard was being led to the waiting police van. 'Everybody okay? Are there are others that we should know about?'

'Guard knocked unconscious and handcuffed to the fence behind the skips in the car park,' John said, 'That's it.'

'Self-defence, I presume?' Lestrade said, nodding at David.

'He had a knife,' Kate said, 'he said he was going to send me back to Sherlock in pieces.'

'The bitch shot me,' David shouted.

'Yes, she did,' Lestrade said, 'but given that I suspect that your finger prints are all over the knife on the floor there, and that I'm sure that the forensics of the cut on her cheek will show that it was inflicted by that knife, I would advise you to keep your mouth shut. Self-defence it is, and no lawyer in the country could get you off this one. You're looking at kidnap, actual bodily harm, and knife crime, on top of providing financial assistance to a known drug dealer and some not insignificant insider trading. If you get out of prison before your sixtieth birthday I would be extremely surprised.'

As the paramedics arrived, Lestrade finally let Sherlock and Kate escape to the waiting police car. Forensics swabbed and photographed her face before John was allowed to close the wound with steristrips. As Kate had suspected, it wasn't deep, but it was enough to justify her self-defence with the gun, and to get David a serious prison term.

...

Giving statements at the police station seemed to take hours. Finally arriving home at Baker Street she asked Sherlock, 'How did you find me anyway?'

'Your watch,' he said. 'Its got a microchip in it, linked to a location website, it let me find you via GPS.'

Kate looked at him suspiciously. 'You gave me a watch with a chip in it and you didn't tell me?'

'Yes. Do you mind.'

Kate considered. Six months with Sherlock had taught her to employ logic first and then consider her emotional response later. 'No,' she said, 'surprisingly not. After all it potentially saved my life, but why didn't you tell me?'

'Because after David I assumed that you would think of it as controlling behaviour and would have quietly elected not to wear it. Was I wrong?'

Kate considered again. 'No, you are right, as usual, I wouldn't have worn it.'

'So am I forgiven?'

'For rescuing me yet again? Yes, I think so.'

Lestrade was also correct. David got a total of twenty five years for a long list of crimes, including all the ones that Lestrade had listed. Several of the Chinese Drug Barons also found themselves implicated and serving custodial sentences.

'I don't think that we'll be able to have dinner in Chinatown for a while,' John said, not without regret. How long do you think their memories are?'

'Long enough,' Sherlock said, 'although I think that most of the restaurants there are relieved to not be having to pay their dues there anymore, so I don't think we'll have to stay away for too long.'

Kate kept wearing the watch, after making Sherlock promise to only use the tracker at times of dire emergency. Because she trusted him, because she knew that he wasn't David, and because when you were living with Sherlock Holmes you never knew what danger was lurking around the corner.