Once doubt creeps in, once you stop trusting the other person entirely then the cracks start to appear. Kate knew this from previous relationships, and yet the doubt that Mycroft had planted in her brain began to grow, despite all of her attempts to stop it.

She was strangely relieved when John, not Sherlock, was waiting for her outside work that evening.

'You get me today, sorry,' John said with a grin. 'Sherlock's trawling through a whole load of cctv footage from outside Highbury station, trying to find the car that abducted Jamie Drayton.'

'Did Greg Lestrade catch up with you?'

'Yes, thanks for the text - Sherlock was all for doing it on his own, he's so pissed off with Mycroft, but his smugness about being right about Jamie Drayton's murder over-rode that.'

'Any post-mortem results yet?'

'Early days, but single shot to the back of the head by the sound of it.'

'Professional job then.'

'We think so.'

'John, why does Mycroft want Sherlock to investigate this? The police are involved now, his own men too, why bring Sherlock into it?'

'I suspect because he thinks that it might be an inside job - he's keeping the secrets service guys at arms length, thats for sure. We've hardly seen them, and thats unusual. Usually they're telling us off for treading on their toes.'

'Did Lestrade tell you about the assault too?'

'Yes. Interesting. It ties up with another of Sherlock's theories, hence my somewhat eye-opening afternoon touring the local gay bars. You'd be amazed at how many of those places are open at lunch time.'

'Did you find anything?'

'Several people recognised Jamie's picture, although unsurprisingly they had known him by a different name. Turns out there was a boyfriend, one that only arrived on the scene a few weeks ago. South American we think. Lestrade is trying to identify him from the cctv footage.' John showed her a picture on his mobile phone, captured from the cctv.

'Quite a catch for a man like Jamie,' Kate said, looking at the undeniably beautiful man in the picture. 'Honey-trap?'

'Seems likely, doesn't it.'

'John, ' Kate hesitated, 'Did Lestrade tell you that Mycroft came with him to see me at work today.'

'No, although I thought that he sounded a bit evasive,' John said. 'Can't say that I'm surprised. How was he?'

'Fine. Odd.' Kate said with a frown. 'He told me that he was worried that I would destroy Sherlock.'

'Did he say why?'

'No.'

'He's talking rubbish, Kate. Sherlock is happier than I've ever seen him.'

'Really?'

'Its not like you to be uncertain,' John said with a sideways look at her as they walked towards the tube station. 'He hasn't got to you has he?'

'No, of course not,' Kate said, then, 'John would it be wrong not to tell him unless he asks? I don't want to lie to him, or go behind his back, but just - from his reaction yesterday, I don't want to upset him, and if he walks away from the case again its just going to give Mycroft more ammunition, isn't it?'

'You're asking me for relationship advice Kate?'

'Yes,' Kate said bluntly. 'What would you do?'

John considered carefully. 'I wouldn't volunteer the information unless it comes up in conversation, but I wouldn't lie to him either,' John said finally. 'You were right last night. Trust is a huge thing for him, don't do anything to betray that trust.'

Kate nodded. 'It sounds as if he's too distracted by the case to think about Mycroft anyway.'

'Don't you believe it,' John said darkly. 'He's been ignoring his phone-calls all day and making me do the same. Thats why Lestrade had to phone me.'

'So he's still angry?'

'Furious I would say, but he's successfully ignoring it and focusing on the case, just like he always does.'

'Another reason not to rock the boat?'

'I'd say so,' John said frowning slightly, 'I've never seen him so unsettled by Mycroft, Kate, its not like him.'

'Then the last thing that I need to do is to make it worse,' Kate told him, as they walked through the ticket barriers, tapping their oyster cards as they went. 'I just wish that Mycroft will back off.'

'He will eventually,' John told her. 'He did with me - tried to warn me off, but eventually he seemed to decide that I was a good influence. Its when he starts phoning you to get messages through to Sherlock that you need to start worrying.'

Kate shuddered at the prospect.

...

Arriving at the lab, bag of sandwiches and coffee in hand to compensate for Kate's missed lunch, which she realised was still sitting abandoned on the desk in her office, they found Sherlock humming cheerfully to himself as he alternated between a rapid progression of slides on his microscope, and the notes that he was writing in indecipherable hand writing in the work book next to him.

He looked up and grinned broadly at Kate as she walked in the door, 'Is that food? I'm starving,' he said uncharacteristically as she came over to the bench and kissed him hello, John diplomatically busying himself with checking the computer for new emails.

'If you're thinking about food then things must be going well,' Kate said, handing him a sandwich and a coffee. 'I'm assuming that you didn't get any lunch either?'

'Why what time is it?' he asked, as if surprised that the day had gone so fast.

'Just after six,' she told him, pulling up a stool next to him, his arm still firmly round her waist, as if he had forgotten about it. 'So what have you found?'

There seemed little point in suggesting that sandwiches and chemicals didn't mix as he devoured his food, while continuing to consider the sample under the microscope.

'Have a look,' he said, pushing the microscope across to her.

'Clothes fibres,' she said, relieved that she could recognise what she was looking at.

'Clothes fibres that match the suit that Jamie Drayton that he was wearing when he disappeared.

'Found in the tube tunnels?'

'Exactly, and we've got a match on the car we picked up on cctv too, John. Registered to a Walter Smith, obviously an alias, but spotted behind the flat of a well known crime syndicate three days before, and then picked up on CCTV heading out of London on the M 40three hours later.

'On its way to Wales?' John asked, joining in the conversation, and coming over to claim his own sandwich.

'Exactly,' Sherlock said. Then with a sigh, 'But it almost seems too easy, too neat, doesn't it? Lestrade phoned. They've identified the man in the cctv from the bar that you picked up this afternoon, John. He came into the country on a false passport two months ago, only a week before he was first spotted with Jamie. He's got a police record as long as your arm in Brazil. Seducing both men and women and disappearing with large sums of their money is his speciality, although recently he's branched out into slightly more violent variations of this.'

'So was he involved in the attack on Jamie?' Kate asked confused, 'but the dates don't match up do they?'

'The attack was five weeks previously, but almost certainly related,' Sherlock said, looking between Kate and John to see who would make the connection first.

'You're saying that someone arranged for him to be attacked, so that he would be an easier target for the softly, softly approach by the Brazilian beauty?' John said incredulously. 'You've got to be kidding. What sort of sick individual -'

Sherlock shook his head, 'This is not a pleasant world, John, you know that. It would appear that that is exactly what happened. The man involved in the attack had never been seen at that bar before, or since. He went in there, made a bee-line for Jamie, almost certainly spiked his drink and then later got a little rough. Part of Luiz Costa's appeal was that he was everything that Jamie's attacker hadn't been. Gentle, kind, protective. The perfect honey-trap I would say.

'So what was it all for?' Kate asked. 'Information?'

'It would appear that Jamie was working on more than the standard GCHQ analyst,' Sherlock said, 'although Mycroft won't give me the details. Only that it is information of importance to National Security. Whoever kidnapped Jamie Drayton was playing the long game.'

'Did they get the information that they wanted?'

'We have to assume so. They wouldn't have shot him unless they'd got what he wanted. Mycroft is working to seal the leak. They're already trying to track down Carlos, but we know nothing about the other members of the gang. Our best bet is to track them through Wales, discover where they took Jamie and see what forensics we can reclaim from there.'

'You've talked to Mycroft?' Kate asked, wondering if he had told Sherlock that he had been to see her. The impassivity of Sherlock's tone and the lack of anger told her that he hadn't. 'Mainly texts,' Sherlock told her. 'I find it less - irritating, than speaking to him directly.'