A/N Um… Hi. Sort of been AWOL for a while... bit more than a while, tbh.

Anyway, this is my tag to TST, because I couldn't sleep until I'd written it and I thought I might as well post and see what everyone else thinks before it becomes AU when TLD airs. Please bear in mind that it was 4am when I finished this so my brain may or may not have been involved.

Disclaimer: I am not Mofftiss or the BBC and sadly I am not making any kind of money out of this.

Warnings for emotional infidelity and a thoroughly screwed up John's strong language.

000

The Four Year Problem

John stirred sluggishly from where he'd dozed off on the couch, feeling as if he'd slept rather longer and more deeply than usual. He rotated his bad shoulder with a grimace, peeling his eyes open to see his front room… and blinked, certain something very strange was happening.

The last thing John remembered was setting Rosie down in her swing chair after a change and downing half a cup of lukewarm coffee in a bid to stay awake long enough to do the laundry. They were down to a dangerously low level of clean Babygros and the baby seemed to soil them with food or sick or poo every hour. After that, he needed to run to the shops and get some more nappies and sterilising fluid for her bottles, and possibly some food for himself while he was at it. By then, it would be time for Rosie's next feed, and then he'd have to try and get her to sleep before trying to do something about the state of the flat, which was reaching 221B levels of chaos, if Sherlock had ever had a case which required him to litter the whole place with baby paraphernalia. Possibly using a cannon.

At the moment, he was torn between thinking that this was either some kind of bizarre dream where his flat had been visited by house elves, or that he'd suddenly taken up sleepwalking. The room was immaculate; toys put away, coffee cups and abandoned sandwiches missing from the coffee table. It had even been hoovered. There was a small mountain of new packages of nappies waiting by the changing mat and he could hear the tumble drier humming as it worked. Also, when he'd sat down John was fairly certain it'd been about ten thirty in the morning. The curtains were drawn now over clearly darkened windows; he checked his watch and stared incredulously, certain it couldn't actually be quarter to midnight. Rosie's crying should have woken him hours ago, and there was no way he wouldn't have heard her, unless…

The swing chair had been put away in a corner. It was damningly, terrifyingly empty.

The door to the nursery opened to reveal Sherlock Holmes in rolled up shirtsleeves, muslin slung casually over one shoulder as he cradled John's daughter, rubbing her back gently with one hand while somehow managing to keep hold of her empty bottle with the other.

"Ah, and Daddy is awake at last," he said. "I was starting to worry about Wiggin's dosages. See, Rosie, I told you he'd be fine."

"Sherlock," John rasped, hoarsely.

"John. I'm sure you'd like to start shouting at me, but I'm equally sure you'd like the baby not to be a part of the inevitable altercation. I am likewise aware that you haven't showered in four days and have just awoken from the longest period of uninterrupted sleep you've had since she was born. Also, there are at least three vomit stains on your jumper and baby food mashed up your left sleeve. I therefore suggest that you spend the next fifteen minutes freshening up while I put her to sleep, as I doubt the extra quarter of an hour will make much difference to her at this stage."

"Or, you could give me my daughter in the next ten seconds and get the fuck out of my flat," John snarled. "And maybe I won't break both of your arms for daring to lay so much as a finger on her."

"John, please." Sherlock sounded almost despairing. "Don't make me resort to holding Rosie hostage just to have a conversation with you. I'll take the broken arms if I must; it's no less than I deserve."

Throughout this exchange, Sherlock's hand had never stopped moving on Rosie's tiny back. She burped, the sound surprisingly loud in the tense atmosphere, snuggling closer into his shoulder. Her opinion on Sherlock's presence was as clear as a pre-verbal infant could make it.

"Fifteen minutes," John said curtly, trying not to let the pang of jealousy become audible in his voice. "No more."

When he returned from a quick but welcome shower, dressed in a pair of jogging bottoms and a jumper (which he knew had been covered in baby wee and mashed rusk respectively this morning and were now miraculously clean, dry and neatly folded) Sherlock, somehow, had managed the impossible and got Rosie to sleep, tucked into her cot. John stepped into the nursery, drinking in the sight of his daughter, so blessedly peaceful. He couldn't help but feel at least a little impressed at how much Sherlock had managed to achieve while he himself had been dead to the world… until he remembered the comment about dosage.

Sherlock was fussing about in the kitchen, setting a single place at the table while the microwave hummed and the kettle came to the boil.

"Mrs Hudson made one of her casseroles," he said, a little too fast, as if he were nervous. "She's been worrying about you not taking the time to eat properly, but her hip was bothering her so I said I'd bring it round. Do you want tea or coffee?"

"Depends." John ground out. "Which one is laced with Wiggin's knockout drops this time?"

"Neither," Sherlock replied seriously, making sure to meet his eyes. "I…"

"Promise?" John finished. "Because we all know exactly how good you are at keeping those, don't we?"

Sherlock actually flinched, looking down at the table as if in shame. "I have no intention of drugging you again, John," he said softly.

"What part of I don't want to see you did you not understand, Sherlock? Hmm? What part of that was an invitation to turn up at my flat, drug me unconscious and turn into a sodding domestic goddess while I drooled on the sofa cushions?"

"I wanted to help." Sherlock sounded almost meek.

"I think you've helped quite enough, don't you? Get out."

"John…"

"No, Sherlock. No buts, no excuses, no deductions. This is my home and you are intruding. Leave."

"You can't do this on your own, John." The detective said softly.

"And whose fault is it that I'm having to try, again?"

Sherlock flinched. "I know you are angry, and I thoroughly deserve it…"

"Oh, well spotted," John barked sarcastically, folding his arms.

"But you need all the help you can get, particularly after you have to go back to work. I'm not asking you to forgive me or be my friend again, but if you can tolerate my presence in the flat for a few hours while you're sleeping or running errands…"

"And you'll, what, give up solving crimes and become Sherlock Holmes, Consulting Babysitter?"

"I will be here when you need me. Case or no case."

"And you think that if you volunteer to change Rosie's nappies and do the washing enough times, I'll be so pathetically grateful I'm suddenly going to forgive you? For breaking your vow? You think that's enough to make up for getting my wife killed?"

"No, of course not, John. I just… I want to help."

"Oh, I see. Well, there is a problem I'm having right now, as it happens. Posh tosser with ridiculous hair hanging about in my kitchen even though I've clearly told him to sod off. Don't suppose you could be persuaded to help with that one?"

"Mary…"

"Don't say her name, Sherlock," John interrupted harshly. "You don't deserve to ever say her name again."

The detective couldn't bear to see the pain and anger in John's eyes; he fixed his own on the doctor's socked feet instead. "She asked me to look after you, if she couldn't. Both of you. And I will, even if you break every bone in my body for it. I deserve that and more for failing her."

"Don't you dare play the martyr with me, Sherlock Holmes."

"I'm agreeing with you that I am a despicable human being. How is that playing anything?"

"Oh, you're always playing. The Game is on, right?"

"For God's sake, John, this isn't a game! I know exactly what I did and I hate myself for it even more than you do and I have to do something to make it up to her because…" Sherlock faltered, swallowed hard, and forced himself to continue more quietly. "Because I loved her too."

"You loved Mary? Then why the hell didn't you bloody marry her!" John yelled back. "You might as well have; two peas in a sodding pod!"

Sherlock blinked, startled. "What? You can't possibly think I meant…"

"Oh, no, of course not; you're above all that, aren't you? So it was perfectly fine for you to swan off with your favourite ex-assassin when a case got too complicated for your thicky blogger. I could just mind the baby or go to work or watch fucking telly!"

"You can't seriously have been jealous of my relationship with your wife…"

"No? Then how come I was cheating on her!" John screamed.

A whimper from the nursery caused both men to freeze, suddenly aware of how loud their voices had become. When Rosie seemed to settle, Sherlock replied in a much quieter, entirely even tone.

"You weren't cheating."

"Yes, Sherlock, I bloody was!" John hissed furiously.

"No. You were carrying out a harmless flirtation, mostly via text message, with a fellow commuter you met and conversed with on your twenty-three-minute bus ride to work three mornings a week. You saved her on your phone under the initial E; not very subtle. Full name Emily Anne Robertson, 32, from Lanarkshire, worked in insurance. You never bought her coffee, went on a date that didn't take place on public transport or so much as held her hand, let alone took her to bed. You broke it off and probably planned to confess all to M…" He stopped short of completing the name. "But, well, events overtook you."

"You knew?" John pushed a hand through his hair in frustration. "Oh, of course you knew; you're Sherlock Sodding Holmes."

"So did she," the detective informed him, almost in a whisper.

John actually rocked on his feet, grabbing the back of a chair and leaning over it to brace himself. He took several deep breaths before speaking. "Mary knew, about Emily. Well, I might have guessed that one, mightn't I; you two always seemed to know bloody everything. So was that another thing the geniuses only club chatted about then? How long it would take before I felt too guilty and confessed? Did you place bets?"

"Of course not. We both understood. You were feeling trapped, stifled, stuck between me, Mary and Rosie. You wanted something that was just yours, something you had control over. Plus, when your wife is as deadly an assassin as Mary, even considering cheating on her is an extremely risky venture; no doubt it appealed to your pathological need for danger."

"Oh, yes, because that makes it all my fault again, what a surprise!"

"No, it was ours. You resented both of us for lying to you so you decided to have your revenge by lying to us. Mary understood you were still angry about AGRA…"

"Yeah, her initials; which turned out not to be her initials after all. Just another in the long line of things she was lying to me about! I talked to Emily because I was sick to the back teeth of feeling like a third wheel in my own fucking marriage! Just nice, reliable John doing as he's told while the two of you ran my whole life between you and told me comforting lies so I wouldn't overheat my tiny little brain! Lie after lie after lie!"

"We were both trying to protect you."

"And neither of you ever bothered to ask if I wanted protection, did you? I'm forty-four years old, Sherlock, I'm a doctor and a soldier and a bloody good shot! What right do you have – what right did she have – to treat me like another kid?"

"Neither of us ever treated you like a child, John."

"Oh, no, you just took a leaf out of the Mycroft Holmes book of caring," said John viciously. "Go to big brother for tips, did you? Or did you just follow his example from your junkie days? Oh, sorry, your earlier junkie days, because you've never really stopped, have you?"

"We protected you because you're the most valuable asset! If anyone has a chance at raising Rosie properly, it's you; let's face it, you're the closest one of us to normal, as you're neither a sociopath nor an assassin. She needs you more than anyone else."

John's knuckles had gone white on the chair back. "You… you utter… I had it right, didn't I? All those years ago, at Bart's, before you made me watch you chuck yourself off a roof. You really are a machine, Sherlock, if you think you can use my daughter as an excuse for what you did."

"It's not an excuse, John, I'm not trying to excuse anything. I wasn't fast enough, or strong enough, or clever enough, to save your wife and I'm sorry, I'm so sorry…"

"Me, too," John ground out.

"But I can't watch you suffer and not try to do something about it."

"Then why don't you just sod off on another one of your undercover missions, just like you did last time you wanted to protect me!"

"John, the circumstances are entirely different…"

"Oh, yeah, this time you haven't got a round the world criminal empire dismantling jaunt to entertain you. Because God forbid Sherlock Holmes should ever be bored while he destroys my life, again!"

"Again?" Sherlock spluttered. "But I didn't, I mean, apart from… And… oh." His eyes widened in shock, then narrowed in confusion. "Oh, that's… that can't be right."

"Of course it wasn't bloody right!"

"No, I mean… when you said… what you said earlier. I thought you were jealous of my relationship with Mary, but that's not it, is it?"

John let go of the chair, scrubbing a hand across his face. "Oh, for fuck's sake, Sherlock, can't you stop sodding analysing every word I say for one bloody minute?"

"I had it the wrong way round. You were jealous of her relationship with me."

"Sherlock, I am warning you…"

"I'm right, aren't I? You said it yourself; Mary and I had a lot in common. Is that what drew you to her, initially? She reminded you of me?"

"Don't you dare, Sherlock Holmes, don't you bloody dare…"

"And you fell in love with her, married her, had a baby with her… which means… must mean, can't be anything else…"

"Shut up! Just shut up, for once in your life, just, don't."

"Before I jumped off Bart's roof, you were in love with me."

The silence that followed was deafening.

"Oh, well done," said John bitterly. "Lightning deduction, that one; it only took you four years."

"It never seemed an even vaguely possible scenario before."

"Well, congratulations on cracking another problem. Now sod off and leave me alone."

"John… I…" Sherlock was at a loss.

"Don't bother," John cut across him. "All right, if you're so desperate to help, knock yourself out. As long as I don't have to see you or speak to you, do whatever the hell you like; you will anyway."

"John, please…"

"Make yourself my house elf if it makes you feel better, Sherlock, because what you want is always the most important thing, isn't it. I'm going to bed." With that, John stepped into his bedroom and closed the door firmly behind him.

Sherlock didn't move a muscle for a long time, until he heard Rosie start to stir again. The Consulting Detective let himself out swiftly before John could emerge from his and Mary's… from his room to attend to the fussy baby, pausing just outside the flat to pull on his coat and scarf.

The chilly night air made him suddenly aware of the twin trails of moisture on his cheeks.

000

Sorry for the depressing ending. Personally, I don't see John as the type to cheat, but I'm hoping this explains at least one reason he might be tempted. I might continue this if people are interested, depending on how inspired I am by the next episode, but I don't see it getting happier anytime soon.