I find it interesting that we've been shown so many people appearing in Sherlock's mind palace - Mycroft, Molly, Irene, Moriarty, even Anderson - but not John. Sherlock heard his voice inside his head in TEH, so we know John's got to be in there somewhere. But where does Sherlock keep him? And when does John come out to play if not to help Sherlock survive from a mortal wound?

Take this anywhere you want - to a lush sex dungeon or a secret treasure vault hidden in the deepest reaches of the palace. Just make me feel. :)