A/N: This was loosely based/inspired by "I'd Do Anything" by Simple Plan and it wouldn't get out of my head. As for the ending, there's no official date, as such, but that is the most widely accepted one. I hope you enjoy!

Sherlock lay in the dark, dingy room of the cheap hotel he was currently hiding in. As exhausted as he was, his body wouldn't let him sleep. He jumped at every twitch of the curtains moved by the air flowing out from the AC, every creak and rattle of old pipes and worn walls and every flicker of the exterior light coming in through the window.

The day hadn't gone according to plan (again) and Sherlock had switched roles from hunter to hunted. He was fairly sure that Moriarty's men wouldn't be able to find him, for the night at least, but today had been evidence to the fact that things could change in a split second; the moment you believed you were finally safe was the moment you were in the most danger.

Since he had often found himself in such a situation while on the run, Sherlock had found a way to relax his mind without actually sleeping: he wrote letters in his head. Usually to Molly. She had been the last person he saw before leaving London and he had trusted her so much. He still did. It had been almost a year since he had seen her and there had been so much he had wanted to say, but never got the chance; he had to plan every detail with Mycroft and then he was rushed out of London so fast that he didn't get to say a proper goodbye. He knew he would return one day but that didn't stop his brain from conjuring up imaginary scenarios, conversations in which he had all the time in the world to explain to Molly Hooper exactly why she was so important. And that was what his brain especially liked to do on the many occasions when he couldn't sleep.

He closed his eyes and imagined her there in the room with him, sitting on the end of his bed like his mother used to do when he had nightmares as a child. He could see her long hair tied back in a ponytail and her white lab coat glowing white in the dim light. She rested her chin in her hand and turned to look at him. She was always smiling, shyly. Sometimes he allowed himself to smile back.

—||—

Molly was having trouble sleeping, not that it was unusual anymore. Not since Sherlock had left. He had stayed at her flat for a few days while he and Mycroft had sorted out the details of his death and then of his mission around the world - they hadn't told her much - before packing up on a cold, grey morning and disappearing from London to who-knew-where. That was almost a year ago.

She lay awake wondering, as she often did when she couldn't sleep, where he was and what he was doing. She knew, of course, that he was working to dismantle Moriarty's crime network but her concerns were of the more practical kind. Had he eaten recently? Slept? Did he know who he was looking for? Was he tracking them or the other way around? And, most importantly, she wondered if he was safe.

All of these thoughts swirled around in her brain and, in the dark, she felt like she could hardly breathe. She rolled over and checked her phone, the sudden brightness shooting through her eyes. She blinked until the tears cleared and she could just make out that, as expected, there were no new messages. And that it was 3:16. She rolled back over and tried to feel tired again but couldn't manage. Instead, she got out of bed, went to her desk and switched on the lamp. She pulled a fresh sheet of paper out of the drawer and wrote the date at the top: January 6, 2013. If she couldn't sleep, she might as well write. She sat back and wondered how she was going to put everything she wanted to say into this letter. How could she possibly explain everything she needed to?

—||—

Dear Molly, they were always letters for reasons that Sherlock didn't quite understand.

I can't sleep. I don't know what time it is and I've only a vague idea of the date. Sometime in early January, I think. I'm hungry. I should have brought food but I didn't want to stop anywhere for too long and now I can't leave again. It's too risky. Whatever. I've been hungry before; it won't kill me. Obviously, it will eventually, but not yet. It's certainly not going to stop me.

—

Dear Sherlock,

I don't really know why I'm doing this but it seems a bit more productive than trying to sleep when I know I won't be able to. I'm wondering where you are and hoping that you're alright. And not just alright but that you've actually eaten today and slept recently. You probably haven't but I hope you have. You can't fight crime on an empty stomach. Okay sorry, you probably can but that doesn't mean you should.

—

I could tell you about my day but I'd much rather have news from London. What did you do today? Were there any bodies I would have liked to examine? I hope no one has been messing around with my experiments. Or my microscope. Are you still helping Lestrade with cases? Have they even solved any without me? I hope there haven't been any really good ones; I'd hate to miss them.

—

Anyway, I don't even know why I'm writing you a letter since it's not like I can send it to you. Well, I've started now so I'm going to finish. I don't know what else to say so I'll write about my day. Not exciting, I know, but I don't have much else. I had three autopsies today - technically yesterday - all the same case. Lestrade thinks we've got a serial killer on the loose. Sorry you're not here since you'd probably enjoy it. All the victims are young women, all from Sussex and all have strange marks on their necks like snake bites or something. The newspapers, of course, have nicknamed the killer the "Sussex Vampire". Ridiculous, but you still might have enjoyed it.

—

I miss…London, Molly. I miss Baker Street, I miss my skull. I miss John and Mrs Hudson. She brought me tea and biscuits in the morning. I have to get my own tea and biscuits now so I mostly don't. I miss those too. And, Molly, just say it - no one else can hear you, not even her, I miss you. I miss being able to use the lab whenever I want and I miss you sneaking me body parts even though you really didn't need to sneak because you're in charge of the morgue. I miss letting you sneak them. I think it made you feel rebellious. I miss you smiling all the time, even though sometimes it was irritating. People don't tend to smile at me anymore. Mostly growl and frown. To be fair, they want to kill me and you didn't, but still.

—

Just write it down. He's never going to see. I miss you, Sherlock. I mean, I didn't like that you fake-complimented me to get into the lab and there were times I wanted to kill you just to stop the hurtful things you'd say, but I miss working with you. Not with you, but at the same time. And, just for the record, no one has touched your experiments OR your microscope, I've made sure of it. I don't know when you're coming back but I know you'd want them left alone. I miss sneaking you body parts even though I'm in charge of the morgue. I didn't have to sneak them, of course, but I think it helped you feel like you were being really subtle and covert, like a spy.

You know, I wish you hadn't left so fast. I mean, I know you had to so that you had time to get away before Moriarty's network realized you were leaving but I never got to say a proper goodbye. By the time I knew what was happening, I was talking to a closed door. You probably didn't even hear me. But I said it, Sherlock. I said goodbye and I said good luck and I said so many things that you didn't hear and you'll probably never know. I guess I can write them here. I think I need to. No better time than the middle of the night, right?

—

I have to say, Molly, I'm sorry I left in such a hurry. Mycroft and I had planned for more time but…things changed and I had to leave as soon as possible. As such, I never got to thank you properly for everything you did for me. Not just with the actual body switching but for letting me stay with you while we finalized the details. For putting up with me all these years despite the lack of proper and genuine gratitude. For continuing to be someone I could rely on, no matter what, even though I've often been anything but kind in return. Thank you, Molly Hooper. Thank you so much. I'm not very good at these sorts of things, you might have guessed, which is why I avoid them. I can't tonight, though. Even if I can never admit them to you, I have to admit them to myself. I think I need to. Strange things happen during the witching hour, after all.

—

I love you, Sherlock. I know you don't want to hear that or can't or whatever. That's fine. I understand. But I need to get it out. I've written in my diary - oh goodness, thousands of times probably: we've known each other a long time. But I've never written it in a way that you could know. You still won't because I can't send this letter since I don't know where you are, but I need to pretend that you could know. Just for tonight. Now don't go thinking it's because you're a genius detective. I mean, you are, but you're so much more than that.

You say that being on your own protects you, but you just faked jumping off a building to save the people you care about. You say that you don't have a heart, but you left your home to hunt down those who hurt others. You pretend to be arrogant and proud - okay, you are arrogant and proud - but I think you're actually insecure and terribly afraid of rejection. You ignore people before they can ignore you. You say you're a high-functioning sociopath, but I think you want a reason for them to stop prying because if they dig even a little, they find that you're not as cold as you appear. Mycroft has told you that 'caring is not an advantage' and you tell him that you don't. But I think you do. I think you care so incredibly much that you can't even see it yourself.

—

I know you want me to tell you that I love you, but I can't. Because I don't, Molly. But don't let that distract you from what I'm about to say. You are a remarkable woman, Molly Hooper. I know you don't see this but I do. I always have. You're absolutely brilliant but you don't hold it over people, something I never managed to learn. You are quiet and humble and want to make people feel good about themselves even when you don't feel like you matter. You care so much, Molly and it's beautiful. You don't see people the way they want you to see them, but how they really are. This has, for me, been a rather embarrassing revelation considering all of the times you've seen me in a…less than desirable state. And yet, you've loved me all this time. Of course, I know, Molly. How could I not when it shines so brightly through your beautiful eyes and your beautiful smile every time I look at you? You see me for who I truly am and you care anyway. In some ways, you care more than anyone else because others haven't seen me at my lowest. I wish I could return your feelings, Molly, really I do. But that would be unfair to you. I love you but I am not in love with you. To be fair, I will never be in love with anyone. If I was ever going to be, though, it would be you. That I can say. It would be you, Molly Hooper, if it was ever going to be anyone.

—

I'm starting to feel sleepy again, Sherlock. But the good kind of sleepy where you're also happy at the same time. It's silly because I know you haven't read any of what I'm writing, but maybe that's enough for me. Just to have it written down in a place that isn't a diary. I'm going to tuck this away in my desk or somewhere and maybe I'll find it again one day. Or you will. Or whoever owns this flat after me. But it doesn't matter. I've said what I needed to as best I can and I feel so much lighter. At least you can't tell me I'm being ridiculous. I'm really glad I know you're alive, Sherlock. And I can say that in the present tense because I know you'll come back. You'll aways come back because London needs you. John needs you and so does Mrs Hudson and even Mycroft though neither of you will ever believe it. You'll come back because you promised. You promised me.

—

I think I can go to sleep now, Molly, even though Moriarty's men might be right outside. It seems ridiculous but I think just saying those things to myself - and the you that is sitting on the end of my bed - was good enough. At least for now. Maybe one day I'll be able to tell you for real. But I can't afford any distractions now, Molly. Everything must be exact and precise if I want to get back to London in one piece. There's still a huge amount of Moriarty's network out there and no one to do anything about it except for me. But I'll come back, Molly because I made a promise. I made a promise to London, to John and Mrs Hudson and Lestrade. I made a promise to you. So come back I will. I'm sorry you have to lie to John and Mrs Hudson and well, everyone. I'll come back as soon as possible to relieve you of your duty, good soldier, but just hold on for a little while longer, okay?

—

I hope you come back soon though, Sherlock. I don't like having to lie all the time, see the sadness in their eyes whenever your name is mentioned. I don't see much of John anymore but Lestrade always looks so guilty. I wish I could tell him that he didn't have to feel that way, but I know I have to hold on. I think I can, for a little while longer anyway.

—

I know you can't hear me and you're probably quite soundly asleep. I would text you but I don't have a phone since those can be traced so this will have to do: Good night, Molly.

—

Now, of course I know what day it is today, Sherlock, and I wouldn't be a very good friend if I didn't mention it in this letter at all. You probably don't know. Or you don't care. Maybe both. And I know you'd hate for me to remember because the whole thing is pointless anyway, but I don't care. Someone has to. I would text you but I know you don't have a phone with you because they can be traced so this will have to do: Happy birthday, Sherlock.