The Reichenbach Fall." In this regard, the episode was mostly successful.
Emotionally, the episode was pitch perfect. For poor John Watson, it was no small thing to discover that his dearest friend had faked his death and sent him into an emotional hell. Writer Mark Gatiss didn't just let Sherlock off the hook, and got many wonderful scenes out of the situation. The ultimate airing of feelings in the climactic scene was well done, but the comedic moments were even better. Sherlock's poor attempt to surprise John was excellent, and the later montage interpolating "Sherlock back on cases" with "John working at his practice" was a masterpiece.
When it came to the mechanics of Sherlock's return, rather than the emotion... well, that's a murkier area. I love the way the writing played with the audience, starting off the episode with a scenario for Holmes' survival that was largely based on ideas actually debated (even favored) by fans -- and that is promptly dispatched as totally ridiculous. The use of the "Empty Hearse" conspiracy group throughout the episode as a further stand-in for the fans was also fun. (And it allowed us one more fun scene with Andrew Scott as Moriarty.)
Then came the final explanation, at the end of the episode. It was presented in a way that suggested ambiguity,b ut it's my belief that this is in fact the real solution... at least, as the writers intended it. When "The Reichenbach Fall" was written two years ago, they surely knew exactly how they were going to have Holmes survive his fall. They're dealing with the genre of mysteries, and the character of Sherlock Holmes in particular; they simply had to plan their solution. But I don't think the writers anticipated a nearly two year gap before they'd resolve their cliffhanger. It was simply too much time for their puzzle to be picked apart, too much time for suspense to build and build, too much time for the solution to be satisfying. And so they did the only thing they could: acknowledge that no ending would be satisfying. (Cliffhanger resolutions rarely are.)
On the one hand, the way this was handled was an incredibly faithful treatment of the Sherlock Holmes' character. In the stories of Sir Arthur Conan Doyle, Holmes was always reticent about the methods of his deductions. He always bemoaned the simplicity and obviousness of his "tricks," which he knew would seem anything but magical when fully revealed. So it's completely in character for Holmes not to concretely reveal the truth here. On the other hand, the resolution truly was a bit of a letdown, and hanging a bell on it still doesn't alter the fact.
But if I'm at all ambivalent about the cliffhanger resolution, I'm not uncertain at all about the other aspect of the episode, the plot to attack the Parliament. It just didn't work. The episode simply had too much to do in wrapping up last season to make proper room for a new mystery. And if my memory serves, wasn't releasing gas into the Parliament (albeit to poison rather than to cause an explosion) the plot of the lackluster U.S. Sherlock Holmes film? It was definitely the weak link of an otherwise very enjoyable episode.
As always, the performances were stellar. Martin Freeman made us feel the whiplash of a man who had finally moved on, only to be jerked back into emotional torment. Benedict Cumberbatch did even more nuanced work, showing us an evolved Sherlock Holmes who now has a better understanding of friendship in general, and this one in particular. Una Stubbs had a fantastic turn as Mrs. Hudson. Mark Gatiss had some particularly great scenes as Mycroft, bantering with his brother Sherlock. And Amanda Abbington was a wonderful addition to the recurring stable of actors, playing Watson's fiancée Mary. (The fact that Freeman and Abbington are a real-life couple is a fun bit of subtext on the proceedings.)
All told, I'd give "The Empty Hearse" a B+. It was certainly a fine effort, but fell a bit short of the impossibly high bar generally set by the series so far. Still, now that the cliffhanger has been dealt with, I believe the series can get back to business. Or, as the episode so appropriately and thrillingly put it, "it's time to be Sherlock Holmes." I look forward to the next episode.