So Mrs Hudson wash dishes, Lestrade investigates, Molly is in the lab and Watson sports mustaches.
We already knew about the mustaches, from #setlock in fact. We also can imagine what Watson’s doing in fancy restaurant, as it was pointed out, by either Moffat or Gatiss I don’t remember, that we’ve known for one hundred years.
It’s canon (except for Molly). Canon is good (Molly is fantastic).
Also we had already figured out that Watson, John actually, was not going to faint of course, but just to be sure, John is sitting down making it nearly impossible for him to faint (although friend F. managed to faint twice while sitting down). This is not canon but it’s good anyway.
What is completely new here, is that it’s told from Sherlock’s point of view. Not John’s, like it was in Pink, and no third person narrator, like in the rest of the series. Oh wait. Reichenbach ends from Sherlock’s point of view.
This is novel.
We’re going to get to see things through Sherlock’s eyes. And look at them, they’re shiny.