They were back to deadlock - John staring at Mary, Mary staring at John, neither of them wanting to speak first. And so yet again, it was Sherlock who broke the silence.

'Why don't we start with something simple. Who are you?'

Mary turned to him, a sarcastic smile playing on her lips.

'You think that's simple?'

'I very much assumed that it wasn't. Where would you have us start then?'

Mary turned to face John, and something slipped in her face as she looked at him. She went in a moment from being hard, angry, defensive to being - Mary. And she looked afraid and vulnerable, and despite his anger, he had the overwhelming impulse to go to her and hold her close, and tell that everything was going to be all right.

Perhaps something of what he as feeling showed in her face, but whatever the reason, she nodded slightly, as if she had made a decision, then reached inside her coat and pulled out a silver USB stick, which she placed on the table separating her from John.

Sherlock lent forward to look at it. 'A.G.R.A.' he said, reading the black lettering. 'What's that?'

John darted a glance at him. That he was in pain was obvious, but no hint of a deduction? No attempt at looking clever? What was he playing at?

'My initials,' came the reply, and John closed his eyes and looked away, unable to face the cold reality of what she was saying. Her name wasn't Mary, it wasn't even anything close. Who was she then this women that he was married to? And was their marriage even legal if she wasn't who she had claimed to be? John was married to Mary Morstan, a woman who didn't even exist. And the woman sat in the chair next to him, the woman carrying his child - he had no idea whatsoever who she was.

'Everything about who I was is on there,' Mary was saying, and then after a pause, 'If you love me, don't read it in front of me.'

His heart thudded in his chest. Love? She could still talk of love? She still thought that he could love her after all that he had discovered this evening, after all of the lies and the deception. 'Don't you?' the voice whispered in his head. 'Don't you love her still, because isn't Sherlock right? Isn't there a part of you that is a little bit excited by the fact that she is - dangerous - different - secret?'

He lifted his hand towards the stick, then stopped himself, illogically not wanting to touch it. '

Why?' he asked.

'Because you won't love me when you've finished,' she said. And the tears in her eyes were real, and John realised that whatever else she and lied about, her love for him wasn't part of it.

'And I don't want to see that happen,' she finished as John stared at her, wondering what on earth he was meant to do with all of this.

It was Mary who looked away first, and quickly, before he could change his mind, John snatched the USB stick up from the table, and pushed it deep into his pocket. Mary's meaning had been clear. Whatever was on there was for him to see, not Sherlock. And what he chose to share of it would be his decision. But like Pandora's box, once it was open it could not be unopened. The knowledge could never be unlearnt. It burnt like fire in his pocket, and he took a moment to compose himself, slowing his breathing, aware that Mary's attention had turned back to Sherlock.

'How much do you know already?' she asked him.

'By your skill set, you are – or were – an intelligence agent. Your accent is currently English but I suspect you are not. You're on the run from something; you've used your skills to disappear.

An intelligence agent? A spy? Was that was she was? And was that better or worse than an assassin? He shook his head unconsciously, as if he could shake the knowledge out of it.

'Magnussen knows your secret, which is why you were going to kill him,' Sherlock was saying. Of course. Mary's pressure point, Magnussen had been trying to use it to get her to do - what? What had he asked her to do that would make her risk her cover in order to try to kill him. After everything that Sherlock seemed to think that she had done, everything that was on that USB stick, what could he possibly have asked her to do that was so terrible that she would be prepared to risk the life that she had worked so hard to construct for herself for it?

'And I assume you befriended Janine in order to get close to him.'

So even their wedding had been used as part of the plot. John couldn't help feeling a stab of pity for Janine, played for a fool by not one but two of those people she thought she knew best within a matter of months.

'Oh, you can talk!' Mary quipped at Sherlock, as if they were talking about who had nicked the last cigarette from the packet when the others person's back was turned, and Sherlock smiled back at her in acknowledgement that they were two of a kind, both prepared to stoop to any depths to get what they wanted.

'Ohhh. Look at you two,' John interjected sarcastically, unable to cope with their smug self-congratulation, anger rising again. He pointed between the two of them. 'You should have got married,' he said, suddenly wondering if he hadn't inadvertently married a female version of Sherlock. And Sherlock looked - sheepish, as if the thought had occurred to him too.

'Maybe Sherlock was what I wanted all along,' and the voice in his head was John's own this time. 'I lost him, and replaced him with another version of him who I felt was more socially acceptable. Is that what I did?'

He remembered all all those sessions with Ella after Sherlock's apparent death. The number of times she had asked him about his feelings for Sherlock, feelings that went beyond friendship, and he had found himself completely unable to reply. Not because he didn't trust her, but because what he felt for Sherlock was so complex that it transcended the traditional divisions of friendship and love. It had been something deeper, more substantial, more permanent, more soul-defining than anything that he had ever experienced before or since. It had changed since Sherlock's return, but it was still there, that sense of completeness when he was around, that sense of loss when he wasn't. Had he settled for what he could get, knowing that Sherlock was married to his work and had no interest in any relationship outside friendship. Had he - had he...'

John mentally shook himself. Christ, look what she had done to him. He hadn't thought about Sherlock like that in a very long time, why start again now?

'The stuff Magnussen has on me, I would go to prison for the rest of my life,' Mary was saying, and John forced his attention back to the matter at hand.

'So you were just going to kill him?' he asked, still finding it hard to equate the woman sitting next to him, the woman who looked like his wife Mary Watson, who worked beside him in the surgery every day, with the cold-blooded assassin that he now knew her to be.

'People like Magnussen should be killed. That's why there are people like me,' Mary replied, and there was that hardness again that went beyond sarcasm, beyond practicality, beyond the black humour that came so easy to medical professionals as a source of self-defence. It wasn't self-defence for Mary, he had realised that long ago. She just had this uncanny ability to remain entirely emotionally detached from any situation - not like Sherlock. Sherlock had emotional empathy, but not cognitive empathy. He could recognise when people were upset, but not what they would find distressing. He remained genuinely puzzled by emotion. Mary on the other hand, knew exactly how and what would upset people, she just chose to distance herself from it, and seemed to find no difficulty in doing that. Of course she didn't. She had been trained to do exactly that.

'Perfect,' he said, gently punching the arm of the chair. 'So that's what you were? An assassin?'

'How could I not see that?' he asked Sherlock, but for once Sherlock remained silent and it was Mary who replied.

'You did see that,' she said.

And there was the anger again, rising fast in his chest, threatening to overwhelm him.

'And you married me,' she said, and then tilting her head towards Sherlock, 'Because he's right...'

John stared at Sherlock, who looked as if he had never wanted to be right less in his life. Who looked as if he felt responsible for all of this pain that was being inflicted on John, and as if he was devastated by it. Who looked - as if he cared more about this than John had ever seem him care about anything before.

Breaking his gaze away, he turned to his wife. 'It's what you like,' Mary was saying softly, as if she was breaking some awful truth to John. And so she was. She held his gaze for just a moment, and the compassion in her eyes was almost worst than all of the lies and deception of the evening. Christ, how was he ever going to pull his life back together after this?

'So - Mary,' Sherlock was saying, as if realising that John was now incapable of speech.

'Any documents that Magnussen has concerning yourself, you want - extracted and returned.'

What? Sherlock was still going to help her? After everything that she had done? Why? Why not just allow Mycroft to help her disappear?

'Why would you help me?' Mary asked, echoing Johns own thoughts.

'Because you saved my life.'

'Sorry, what?' John asked.

'When I happened on you and Magnussen - you had a problem,' Sherlock was saying, and John watched him slip into deduction mode, but with none of his normal pace or delight in the process.

'More specifically, you had a witness. The solution, of course, was simple. Kill us both and leave. However, sentiment got the better of you.'

Sentiment? She had spared Sherlock because of sentiment? Maybe John was right. Maybe Mary should have married Sherlock. Or had she - could she perhaps have spared Sherlock because she knew that John couldn't have lived with losing him for a second time? Had she realised what John himself was only now beginning to acknowledge?

'One precisely-calculated shot to incapacitate me,' Sherlock continued, 'In the hope that it would bide you more time to negotiate my silence. Of course, you couldn't shoot Magnussen. On the night that both of us broke into the building, your own husband would become a suspect,'

Christ, of course. How had he not thought of that? If John had been the only man left standing in a building full of dead bodies, he would have been suspect number one. Had she spared Sherlock simply to save him that?

'So you calculated that Magnussen would use the fact of your involvement rather than sharing the information with the police as is his M.O.. And then you left the way you came.'

There was no joy in Sherlock's voice in the deduction, only pain, although John suspected that this was as much from his physical injuries as from what he was revealing to John. Mary remained silent, but the look she gave Sherlock showed that he was correct.

'Have I missed anything?' he asked.

Sherlock may not of, but John felt that he certainly had.

'How did she save your life?' John asked.

'She phoned the ambulance,' Sherlock said.

'I phoned the ambulance!' John protested.

'She phoned first,' Sherlock explained. 'You didn't find me for another five minutes. Left to you, I would have died. The average arrival time for a London ambulance is -' he looked at his watch and as if on cue there was the sound of feet on the stairs and a paramedic and a technician burst into the room.

'Eight minutes,' Sherlock concluded breathlessly.

John's mind was racing all over again. Mary had called the ambulance? Mary? She had wanted to save Sherlock after all. It hadn't just been about saving John from being a suspect, she had wanted Sherlock to survive - why? When she must have known that he would never keep silent about this, that he would work out her secret.

'Because she wanted me to work it out,' the voice in his head, Sherlock's voice, said. 'Because she wanted you to see John, she wanted you to know.'

And Mary, Mary was staring at him as if he held her entire future in his hands. And so he did. And Sherlock, Christ, Sherlock was looking waxen. He had seen corpses with more colour. Wherever the majority of his circulating volume was at the moment, it wasn't in his peripheral circulation that was for sure. A fact that the consulting detective seemed to have deduced for himself.

'I believe I'm bleeding internally and my pulse is very erratic,' he was telling the paramedics. 'You may need to re-start my heart on the way,' he concluded, ever the drama queen.

His knees buckled as he tried to stand, and John ran forward to catch him, Mary moving as fast as he did, so that they grabbed him, one on each side to stop him from falling.

'John,' Sherlock said urgently, 'John – Magnussen is all that matters now. You can trust Mary. She saved my life.'

'She shot you,' John pointed out.

Sherlock pulled the face that meant he was aware that he'd made an error of judgement somewhere along the line, and hated to admit that he was wrong. 'Mixed messages, I grant you,' he said, then cried out in pain, and his hand slipped off John's shoulder.

'Sherlock!' John cried out in horror, then, 'All right, take him,' to the paramedics as they gently stepped in to help lower him down.

He stared at Sherlock as the paramedics got to work, placing an oxygen mask with high flow oxygen over his face to ease his ragged breathing, reaching for a cannula and the morphine that Sherlock had been asking for.

And John, John Watson the army doctor, who had always prided himself in keeping his head in a crisis, could only leave them to it, his mind completely devoid of practical knowledge for once. He simply stood and stared across at his wife, wondering why Sherlock was so desperate for him to know the truth that he had risked his life to ensure that John heard the entire truth now, at this time, and in precisely this way. And he had not just wanted John to know the truth, he had wanted him to hear it in a way that might, just possibly explain it, that would enable John to understand it.

'But I can't,' he said silently to Sherlock, knowing that Sherlock was beyond hearing him now. 'I can't forgive her Sherlock, how can I? How can you ask that of me?

'I ask everything of you John. I always have. But you promised to trust me.'

'I do trust you Sherlock. I just don't know how I can trust her.'

'Because I tell you that you can. Because you must.'

John stood there silently shaking his head, staring at the floor now. Vaguely aware that the paramedics had strapped Sherlock onto the trolley, and were now moving at speed.

'Are you coming with us, sir?' they asked John. 'We need to get him to hospital ASAP.'

'You go on, I'll catch up,' John said vaguely, too dazed to move, waiting until he heard their feet reaching the bottom of the stairs, the murmured conversation with Mrs Hudson and the front door closing behind them before finally lifting his head to look at Mary again.

'We both know that you're going to go in that ambulance, John,' Mary said quietly. 'So we'd better do this quickly.'

'Why did he say that I could trust you?'

'Because you can. Because whatever lies I told to protect myself, I never lied about how I felt about you. Can you say the same?'

'So this is all about me now?'

'No - no,' Mary looked down and shook her head. 'I'm sorry, John. You may not believe that, but it's true. I am truly, deeply sorry for the lies that I told you. If you look at that USB stick then you'll understand why I did what I did. Why I had to keep my identity secret - even from you.'

Mrs Hudson's voice came up the stairs, 'John? The paramedics say they have to go now. What do you want to do?'

John could see the flashing blue lights through the curtains of 221b. What did he want to do? His wife and his child were here, and Sherlock was outside. Sherlock had told him that he could trust Mary and somehow he found that he couldn't hate her. He couldn't feel anything other than sadness at everything that he had lost, and it was paralysing.

'John! 'Came Mrs Hudson's voice, 'You have to make a decision now. They need to leave.'

'Go!' Mary said ,breaking him out of his trance. 'John, go with Sherlock! He needs you.'

'How can I?' he whispered, his voice cracking. 'After all that's happened this evening, how can I?'

'Because you don't have to choose, you idiot,' Mary told him, raising a soft hand to cup his cheek., and strangely he didn't shy away from it. 'You never had to choose. Now, go!'

Thank you so much to everyone who has stuck with this story, despite the ridiculously long hiatus. And thank you for the reviews - they are what drives me to keep writing, and I really do appreciate each and every one of them.

And thank you to seven percent, my amazingly patient and brilliant beta, for keeping me on course.

Transcript of HLV courtesy of Ariane Devere.