The acting, casting, direction and production values on Sherlock, as well as the underlying wit and creativity, are uniformly terrific. So what separates an amazing episode, such as "The Great Game" or "The Reichenbach Fall," from a merely great episode , such as "The Hounds of Baskerville" or "The Blind Banker?"

The best installments set up mystery after mystery, giving them a crazy, pinball energy unlike anything else on TV. In "Reichenbach," there are at least 7 distinct mysteries:

1. What's Moriarty's plan to get Sherlock?
2. Why did Moriarty break into the bank, prison and Tower of London?
3. Why are international killers moving in next to Sherlock?
4. Where are the diplomat's kidnapped children?
5. How is Sherlock going to clear his name?
6. How is Sherlock going to save his friends?
7. How the Hell is Sherlock still alive?

OBSERVATIONS AND LINGERING QUESTIONS

- Let's start with the obvious one: How did Sherlock fake his death? It would certainly seem like he enlisted Molly's help to create a lookalike corpse, but how he got it on the roof and fooled Moriarty's spotters is beyond me.

I rewatched his phone call with John a few times, and for what it's worth, it looks like he's calling from a different rooftop - you can see buildings behind him during closeups that you can't see when John is looking up at him, though that could just be a matter of perspective. I also don't think the bike rider who knocks down John is completely a coincidence.

- Sherlock's scenes with Molly, both here and in "Scandal in Belgravia" come off as sad and tender, where they could have very easily been sappy and manipulative in lesser hands. Credit to all involved for elevating them.

-  I was already on the edge of my seat from the tension in the final confrontation between Sherlock and Moriarty, so I was shocked by Moriarty's suicide, even if he hints at it with his boredom about "Staying Alive." I'm sad to see him go, as a worthy challenger to Sherlock, and while it was definitely showy and over-the-top at times, I loved Andrew Scott's performance.

- I'm not quite sure why Moriarty was so adamant about "I owe you" to Sherlock. That he wants to beat him and outwit him, I get, but "I owe
you" has an element of revenge to it that doesn't make sense, unless Moriarty feels like he lost at "The Great Game." Given that it ended with Sherlock and Watson almost being killed by Moriarty, seems like a draw at worst to me, but then again, I'm not a consulting criminal who is a few crumpets short of a tea party.

- I love the second scene between John and Mycroft, the two men who orbit and care about Sherlock, and Mycroft's realization and confession of how he betrayed him, after a little bit of sleuthing by John. But, are we to take it that when they were done with him, Mycroft's shadowy agency just let Moriarty go? Didn't that seem like a bad idea to anyone? He didn't trade information for his freedom, just for stories about Sherlock.

Plus, we know the computer key didn't really exist, so his information wasn't really worth anything. Let's just pretend he escaped and not give it any more thought, shall we.

- Poor John. Great work from Martin Freeman at the start, struggling to talk to his therapist (one of two significant call backs to the
first episode, the other being Donovan's warning that Sherlock will become a criminal). And then again at the grave at the end - really touching how much Watson and Sherlock mean to each other.

- I don't remember the last time I was so eager for a show to return. Maybe after the finale of the first season of Lost? And even then I knew it would only be a few months. Arrggghhhhh...