Fortunately for John, his homeless 'disguise' was pretty convincing. If he was going to get past Sherlock's cameras, without arousing suspicion, he'd need to look like just another junkie looking for a place to shoot up.
He sent a text message to Greg, briefly explaining the situation and giving their location, before pushing open the double doors.
He shuffled through the lobby, hoping his heart wasn't beating as loudly as it felt like it was. He could feel the adrenaline rushing through his system; blood screaming through his veins and drumming in his ears. As he approached the first floor landing, he closed his fingers around the handle of his weapon. Mycroft had once said that when you walk with Sherlock Holmes, you see the battlefield. John couldn't help recognising how accurate that statement could be.
He had no idea what he was going to find on that sixth floor. Sherlock and...who? A contact? More junkies? Moran?
For a moment, John wasn't sure which the worse option was: Sherlock and drugs or Sherlock and Moran. Each had the capacity to be equally deadly to the detective, and John found himself wishing that he'd waited for back-up. He soon dismissed the idea knowing that, once police arrived, the risk to Sherlock would increase dramatically, whatever situation he was in.
John steadied his nerves with a deep breath and continued his climb. Fourth floor; fifth floor... He paused at the bottom of the sixth floor stairwell. If Sherlock was watching for Moran, he would be likely to have a camera set up on the sixth floor too. Being seen on that camera would be more likely to raise alarm than just being spotted in the lobby, but there was little John could do to avoid it. He slowed his approach as he rounded the top of the stairs. There were only two flats without tape across the door, and he could see from the open door of one of those that it wasn't the one he wanted.
John slipped quietly along the corridor, and stopped next to the closed door of Sherlock's flat. He had two options. Knock and wait or burst in. The poorly maintained flat's door frame looked weak, and John decided it probably wouldn't take much to throw it open. Grasping his gun firmly in both hands, he launched himself at the entrance just in time to see a figure huddled over a restrained Sherlock.
As the figure reached for its own weapon, John took aim and fired a single shot...