The Abominable Bride is a "Christmas Special", which in the UK basically means that it's an episode that comes out around Christmas time, but has very little to do with Christmas. This was released in early 2016, and like all other episodes of Sherlock, it's 90 minutes long.
This is one of very few episodes that isn't based on a particular story by Sir Arthur Conan Doyle. It compiles a few references to some of the old stories, but nothing terribly specific to the happenings-on. It's more of an original story to appease the audience in between season three and four, and it does so very well. Unlike the main series, this special takes place in the1800s, just like the originals. It's a very dark, gothic tale that veers into almost horror at times. It's incredibly atmospheric and well-done, from its costumes and backdrops to the actual mystery.
There is a twist in here, but one which I will not spoil. It's something I didn't expect, upon first viewing, but the hints were definitely there upon a second. Needless to say, this sated my appetite until season four arrives (hopefully in January!).
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