On January 1, 2016, "Sherlock: The Abominable Bride" was shown on the BBC. This is a one-off after the third series and not part of the upcoming fourth series. It was notorious before it even hit screens because it threw Holmes (Benedict Cumberbatch) and Watson (Martin Freeman) back to Arthur Conan Doyle's time - even though the entire three series prior had been set in the modern day. The weird thing is ... once you watch this, you'll find it's actually in sequence. Unfortunately, I can't explain that without revealing a whole bunch of spoilers.
The show starts by recapping the meeting of Holmes and Watson - almost identical to that in the very first episode, but all set circa 1890. And so it goes, with most of our current characters all showing up, Lestrade and Mrs. Hudson being most visible. We jump forward, with Holmes an established detective in large part because of Holmes's various stories in (or at least advertised in) The Strand. But the case of interest is, of course, "The Abominable Bride." The script goes out of its way to emphasize the sexism of the period, which becomes an important issue.
I have to admit that I deeply loved the first episode of the first season ("A Study in Pink"), and haven't felt that any of the intervening episodes have come remotely close to that one. This one is pretty weird, and has some distinctly interesting elements. The end product gave me very mixed feelings - I guess that probably means it's worth watching.