As soon as Mycroft had left 221B John walked over to Sherlock's room. He opened the door, knowing full well what he would find. Once John had finally managed to make it back to 221B after that day three years ago he had left Sherlock's room alone. He had cleaned the rest of the flat over the course of a few days, but he was determined to leave Sherlock's room alone. He was determined until he found the syringe behind a loose tile on the bathroom wall.
The syringe confused John at first. He thought perhaps it had belonged to a previous tenant. But of course, he remembered almost instantly, Sherlock had gotten a very strange look when Lestrade had come on a phony drugs bust not so long after John and Sherlock had met. He assumed at the time that Sherlock couldn't possibly have any drugs, the very thought was absurd, but that look unnerved him. Once John held the syringe he knew what Sherlock had been trying to tell him. "Shut up. Not because you shouldn't speak but because I don't want them rummaging around here long enough to find what I've hidden."
The effect on John of finding the syringe was immediate. He clutched it angrily and swore. He cursed Sherlock over and over again. John had trusted him. But now he played the fool again. He had known that Sherlock had his secrets, more than the average person, but this…this pushed John over the edge.
Without hesitation John burst into Sherlock's untouched room and began tearing it to pieces. It took him the remainder of the day to go through the entire room but by the end he had a pile of syringes and a reasonable belief that there weren't any left in the room to show for his efforts. Two days later the pile had doubled, but the flat, John was relatively sure, no longer contained any hidden surprises.
After that John spent a week trying to put the flat back in order before Mrs. Hudson could come and wonder just which of her tenants had truly been the messy one. He had cleaned Sherlock's room in the process, and every few months he returned to dust and keep up the room for…for no reason he could fully form in his mind.
As John entered it now it looked just as he expected and he slowly walked over to the bed. He sat down, sighing as he looked around. If he was going to find Sherlock he'd have to go out into that scene. He'd been there once now, when he had wanted to know what was in the syringes. Going back wouldn't be so hard. He had contacts now, right? Slowly John lowered his face into his hands. How could any of this be real?
For two days John trudged through the back alleys and less agreeable parts of London a clue finally began to lead somewhere. Sherlock's homeless network came through, whispering to John that his best friend had been spotted only two days before entering an abandoned house only a few blocks away. As soon as John was sure of the exact location of this house he turned his back on his informant, forgetting to thank him in his rush to find Sherlock.
John nearly ran to the house, not caring that he bumped into more than one druggie in his quest. They were not important. Sherlock was important. When John reached the house he stopped in his tracks. He stared at the door as though it couldn't be real. Sherlock. Living, breathing Sherlock. Living, breathing, drug using Sherlock. John didn't waste any more time in climbing the stairs to the front door and turning the handle.
The door wasn't locked and John slowly made his way into the dim entryway. The light barely illuminated the crumbling interior. Wooden beams were falling down and cobwebs covered most of the doorways. The stairs were the only area that showed signs of use and John climbed them slowly. He didn't know if he was trying to avoid making noise that might startle Sherlock or if he was still trying to decide if this could possibly be real.
John paused for only a second at the top of the stairs. There was a soft light up ahead and John could feel his mind and heart willing him forward. When he found the source of the light he stopped, a cold shiver running down his back.
"Sherlock."