Doctor John Watson stood in that empty building and yelled. Sherlock. Never had he felt so helpless in his life. Not even in Afghanistan when he was being shot at and blown up. There he had always had his training to fall back on, he could retreat into that place in his brain that the army had drilled into him, become not quite aware, run on automatic. The adrenaline pumping and flowing. The guilty thrill of the action.
Here, what was he supposed to do? There was nothing. He wasn't trained for empty buildings miles high, where the friend (if Sherlock could indeed be called that) and the enemy were across a cavernous gap and two windows, in another empty building. There was no way out this mess, no solution, unless …
And Sherlock was such a damn idiot that he was about to take the stupid pill. By choice. He could see him, even across the gap. Just to prove he was clever. Just to stop the boredom. And so John Watson shot a man, that day, with a pistol he technically shouldn't still have.
Funnily enough, the moral implications of what he had done never troubled him. Murder. He had killed men who had deserved it far less before, watched good friends, good men die. Watched, helpless to save them. He was a Doctor, he was supposed to save lives not watch them die. He had though he would never get over it, the War, the death and the murder. This gave him no such trouble.
What troubled John though was how willing he was to kill for Sherlock Holmes. The man had been in danger, yes, but it had been a danger of his own making, he was willingly taking that poison pill, not because he was under any pressure, not because of a gun pointed at his head, but because he wanted to prove a point. Because he was bored out of his overlarge skull. And yet John had risked everything, possibly even a long prison sentence, to save Sherlock because, for some reason, despite everything, Sherlock was important to him. After only a few days. It terrified him and felt absolutely natural at the same time.
What was it about Sherlock? The man was, in his own words, a 'high functioning sociopath', though John was sure such a thing didn't exist. But the fact remained that Sherlock didn't seem to feel emotions or empathise in the same way a normal human being did. Sherlock was able to feel emotions, to a small extent, no matter how much he tried to deny it. But Sherlock simply didn't seem to consider his emotions, or the emotions of others as important. He insulted John, and everybody else, at every turn, used him as his personal errand boy, and what Sherlock did to the flat would make most people sick.
Perhaps they were right, those insufferable sibling geniuses, and it all came down to the intermittent tremor in his left hand. His psychologist thought it was PTSD, but it wasn't. It was the other way round. He needed the action, in truth, he was just as crazy as Sherlock was, and he was just better at hiding it.