High-pitched notes, moving fluidly through the flat woke John in the early hours of a Wednesday morning. It was the all too familiar sound of a violin, and there was only one resident in 221B with the skill to play such a delicate instrument.

Turning in his bed, the sound of his hair against the pillow momentarily blocking out the beautiful music, and leaning towards the clock on his bedside cabinet, John saw that it was in fact 3:08am. John flopped back onto his pillow, closed his eyes and pinched the bridge of his nose, breathing deeply as he tried to bottle his frustration. This clearly wasn't happening, so he kick his legs out of the bed, and jerkily sung his body around so he ended up in a sitting position on the edge of his bed. It was pitch black, apart from the tiny sliver of light that was slipping through the gap that the slightly open door left.

John had slept with the door open ever since he arrived back at Baker Street, just in case something happened in the middle of the night and John needed to get to Sherlock quickly, although as of yet, this hadn't happened.

John took a few moments, still perched on the edge of his own bed, the sound of Sherlock playing the violin still travelling up the stairs. The air seemed to stir around him at the sound, as if the flat was waking up around him at the sound of the familiar strings, stretching it's walls as it recognised the return of it's detective. John ran his hands through his short, grey-blonde hair – an action that he seemed to be repeating a lot recently. He let out a sigh of resignation and pushed himself off the bed and towards the door.

Fair enough, his friend was suffering, but that did not make it okay for him to wake him up at bloody 3am with his violin playing. He thought that he should probably be delighted that Sherlock was showing signs of normal behavior, but all John could feel towards the situation was irritation. Was it too much for him to get a decent amount of sleep? He made his way down the stairs, his annoyance growing with every step he took towards the music. He reached the bottom of the stairs and turned into the living room, about to give Sherlock a piece of his mind.

But he didn't.

John stopped in his tracks by the sofa as the piece of music that Sherlock was playing finally made it's way through the cloud of irritation in John's mind, and John recognised it.

It was a waltz.

It was his waltz.

It was the waltz that Sherlock had composed for his first dance with Mary.

It was painfully beautiful, just as John remembered it. He closed his eyes and saw Mary, in her beautiful ivory gown, and her smile, such a beautiful smile. He saw the guests, all stood around them as they took their tentative first steps of the waltz. He could see Sherlock, on the stage in his suit, eyes closed, concentrating and letting the music take over him as he played. He could himself together with Mary together, twirling on the dance floor, as Sherlock played his composition for them, such a perfect moment.

John opened his eyes again, and realised too late that they were full of tears. He let the notes wash over him, each one feeling like a knife to the stomach, and yet they gave him hope. Was that possible? How could something give you hope, and yet at the same time cause you so much pain.

The lights were slightly dimmed, as was the custom after 1am in Baker Street – a habit established by Sherlock before John had even moved into the flat. Sherlock was stood with his back to the room by the fireplace, so John was unaware if he knew that John was there. He finished the piece on a long, haunting note, which left a hollow feeling in John's chest. John tried to clear his throat, which had become tight as he wiped away the tears that had now spilled over his cheeks.

"This piece," Sherlock didn't turn around as he address John, nor did he lower his violin, "I don't know it, and yet I hear it, every time I see you and your wife together." He turned around to look at John, who had given up with his attempts to hide his emotions and slowly lowered the violoin until it was at his side, bow in the other hand. "It fills my head, my entire mind palace until it's the only thing I can concentrate on. Why?"

John remained silent, unable to find the courage to speak.

"Why?" Sherlock was shaking, John could see the bow in his quivering.

"Because-" John began, his voice breaking. "Because that's- That's the piece you- You wrote that for us, for our wedding." John had to avert his gaze from Sherlock.

"Your wedding? Yes, I was… There was a man… a mayfly…"

John's head snapped back to his friend. He walked quickly over to him, placing one hand on each shoulder, locking his eye with those piercing blu-green eyes. Sherlock flinched at the touch, but he didn't pull away, allowing John to keep a firm grip on him.

"Say that again. Say that to me again, slowly."

Sherlock's eyes closed and his face crewed up in concentration. H took in several deep breaths before he spoke. Clearly this was taking a lot of effort on Sherlock's part, but John didn't let go, he kept his eyes focused on Sherlock's face.

"A mayfly man, he lived for a day, four – no – five girls, attempted murder." Sherlock dropped the bow on the floor and lifter hi hand to his head. His jaw tightened and John heard him suck in a breath through his teeth. John's hands dropped to his sides, and he took a step away from the taller man, he didn't want to crowd him.

"Go on." John encouraged, his pulse had quickened in anticipation, he could hear the beating of his own heart in his ears, which was probably a bad sign but he chose to ignore it.

Sherlock's hand was pressed painfully against his forehead. John moved forward and removed the violin form his grasp before he dropped that too. As soon as his hand was empty, Sherlock moved it to his head, ramming the base of his hands into his eye sockets. His breathing became quicker, and John feared that he was about to begin to hyperventilate. but before John could reach out to sit him down, Sherlock let out a furious groan, that was so full of rage that John took another step back. His eyes snapped back open.

"I can't. I can't remember anything else." He grabbed the closest item to him – one of John's mugs that had been left on the mantelpiece above the fireplace – and threw it across the room. It missed John by inches, smashing into a hundred pieces against the wall to John's right, but John didn't even flinch, he was too focused on what Sherlock had just told him.

His memories were there. They were there, still tucked up in his mind palace, struggling to get out. The waltz had clearly triggered something that had allowed these small pieces of information to infiltrate through the fog, and bloom into Sherlock's mind like the most beautiful flower in existence. Where Sherlock felt rage at being unable to remember anything else, John felt euphoria that something was coming back to him. Granted, none of it had lead to the uncovering of John's identity in Sherlock's mind, but it was something. A very good something.

Returning to the present, John noticed that Sherlock was now sat in his chair, head dropped in his hands, still shaking. John moved to sit opposite him in his own cushioned armchair. If John was capable of processing any train of thought, he would probably have been amused at the role-reversal that had occurred between himself and Sherlock, as the detective was overwhelmed with emotion and John seemed incapable of processing any emotions.

"Why was I there John?" John blinked a few times before being able to focus of Sherlock's face.

"Why- What?"

"Why was I there? Your wedding? I don't ever go to anything like that, so why was I there? Was I tricked, drugged, or just there to solve a murder?" In that moment, Sherlock had never looked so vulnerable.

"You were there," John managed to choke out, the emotion he was feeling threatening to overwhelm him and close of his throat completely, "because you are my best friend and I asked you to be my best man."

John's words were greeted by a stunned silence as the detective let John's word infiltrate his mind and settle there.

"I was your best man?"

"Yes."

"Why?"

John looked at his hands, once again unable to look into the eyes of his best friend. Why did he always press John like this? John wanted to walk away and drop the subject. But he'd agreed to help Sherlock recover, and if that meant answering every question thrown at him, then John planned to do absolutely that.

"Because you are my best friend, and I didn't want anyone else to stand there with me as I got married, because if it had been anyone else, the role of 'best man' would have been completely meaningless. You were the only one I wanted for the job." John's eyes never left his hands, not even after he finished talking.

The silence between them was like none that had ever been before. The tension could have been cut with a knife, and it was tangible in the air around the flat. John was vaguely aware of movement in front of him, but it was another few minutes before he looked up and noticed the absence of his friend. Turning to see that Sherlock's coat and scarf were also missing told John that he had exited the flat.

Knowing that he shouldn't let Sherlock be running around London in this state, especially after days cooped up in the flat, John ran upstairs and quickly changed, before grabbing his own coat and running out of the door, closing it behind him and into the cold, London air. He turned his head each way down the street, before deciding to try going left first. He set off at a brisk pace, keeping his eyes peeled for a mop of ebony curls on top of a blue scarf and thick, black trench-coat.

John could tell that it was going to be a long night.