I feel like I've cracked the problem of Sherlock's "His Last Vow."
I wrote this at TrekBBS earlier. And we have to go back about a decade, to another television series about a brilliant, drug-addicted man who could discern things simply from observation...
House pulled the trick at least twice of having what appeared to be an ordinary episode turn out to be the fevered hallucination of House. I'm thinking in particular season 2's "No Reason" (the Moriarty episode) and season 5's "Both Sides" (House hallucinates that he slept with Cuddy while on a Vicodin high).
Could some (or all) of "His Last Vow" have been a hallucination on Sherlock's part?
Is it noteworthy that Sherlock was shot? "No Reason" had House in a state of hallucination after he was shot, and given the derivation of House that might be significant.
Could everything after Mary shoots him be imagined? Especially since Sherlock uses his mental powers to keep himself conscious? (Is that what he told himself so that his perception of the narrative would continue?) Did Sherlock have to destroy an imagined enemy in his dreams, just as House did? (Which makes sense of why Sherlock was the one to pull the trigger; it's his hallucination, and he needs to be the one to take action to escape it.) And are the final reveals actually Sherlock "waking up" from his hallucination?
It's not perfect, but this would make sense of the situation. And it would be Moffat paying tribute to the modern day series that paved the way for Sherlock.
Thoughts? Yes? No? Maybe so?