The Truth in the Lie
Summary: He's standing on the edge and there's a point where it all blurs spectacularly together, the lies and the truth and he's not acting anymore. Not completely. Sherlock during The Fall.
There are things he has to do, things he must do. He must orchestrate the biggest lie he's ever told in order to take down Moriarty's network, in order to spare his friends. So he'll use Mycroft and Molly and a team of others, and they'll do it just right. There is, undoubtedly, an elegance to it. He thinks the other him would have liked it very much. The Before-John Sherlock. Now, he logically knows there's no such difference; there are not two people in one, no matter who sweeps into his life, but a bigger part of him says, there is, there is.
Because he's not the same man that he was before he met the doctor, the blogger, the friend.
There was a time when Sherlock had no one to leave behind, no hearts to break. Now there's John, so far down upon the ground, begging with his voice. Telling Sherlock no, he doesn't believe a word he's saying about being a fraud, and no you're not you can't don't.
Sherlock knows he's a good enough actor to pull this off. He can lie at will and whim with no tells, and only the most acute attention of a probably similarly sociopathic nature wouldn't be fooled. The Woman springs to mind. Mycroft too, though Mycroft doesn't count. The point is, John has never been one of them. No, he's too good and decent to always see the worst in people, even if the worst is true. Sherlock has fibbed to him often enough when there has been a need, and John will take it at face value. The only lie he won't accept is this one, that Sherlock Holmes is a fraud. But it doesn't matter, because as long as John doesn't get too close of a look (and no, he won't, their plan will work perfectly, it has to), he will have to learn to believe. The body and the confession will become enough for him in time.
So Sherlock makes sure to play the part quite well, a fraudulent man pushed to his limits upon a rooftop. It all comes easier than it should, especially when he really, really considers the fact that it's a true goodbye. No, it's not permanent like John will think it is, but it's a stretch of indefinite time in which they will be apart. In which John will grieve and Sherlock will try not to think of him. He's never had a friend like John before. He wonders if there will ever be enough apologies in the world for what he's doing now. If he believed in a divine power and that prayer could help in any way, he'd pray now: for John to be safe while he's gone, for John to be strong, for John to forgive him when all is said and done.
As his 'final words' leave him, Sherlock is surprised, or maybe he isn't but knows he should be, to discover that the tears on his face are real.
There are, as it turns out, some things he doesn't have to fake.