Sherlock: The Abominable Bride, on BBC One (UK) / PBS (USA)
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This is a special episode of Sherlock, which unlike the regular series, is set in Victorian times. It's based on a case that was once mentioned by Sherlock Holmes in one of Arthur Conan Doyle's stories, but about which no details were ever given. The special aired in both the UK and the US on January 1, 2016 (between series 3 and 4), with screenings in select US theaters on January 5 and 6.

It begins with Dr. John Watson returning from the Second Afghan War, after having sustained injuries that made him unfit to continue serving. He moves to London, and looks for lodging, finding it as the roommate of Sherlock Holmes. (The whole thing is very like how they met in the present, in the regular series.) The story then skips forward, at which point Watson has been working with Holmes on his detective cases for some years, as well as writing fictionalized accounts of them for The Strand. One night, Holmes and Watson are visited by Inspector Lestrade, who tells them of a woman named Emilia Ricoletti. She had been wearing a wedding dress, and shooting a pair of revolvers at a crowd, before turning one of the guns on herself and blowing her brains out. Some time after that, her husband had been killed, apparently by Emilia's ghost.

Sherlock doesn't solve that case, and some months pass, but then he is presented with another case. A woman named Lady Carmichael tells Holmes and Watson about strange things concerning her husband, Sir Eustace, including the fact that he saw someone who terrified him, but he wouldn't tell his wife who he saw, or what any of this was about. Then just that morning, she saw the woman, herself, and Sir Eustace finally told her it was Emilia Ricoletti. Then the "ghost" said he would die that night. So Lady Carmichael wants Holmes to protect her husband, but Sir Eustace refuses his protection. Nevertheless, Holmes and Watson stake out the Carmichaels' home that night, waiting for the killer to show up.

Beyond that, there's nothing specific I want to say about the plot. (Though I would be remiss if I didn't mention that Mary Watson and Mycroft Holmes both play important roles in the story, as does another character I won't name.) I will say that Sherlock does eventually solve the case, but... there's a twist to the whole episode which I absolutely refuse to spoil. It's not exactly an uncommon plot device, but it's done quite brilliantly, here, and I did think it was a bit of a surprise. Meanwhile, the episode has quite a bit of humor in it, lots of nods to fans of the regular series and of Sherlock Holmes stories in general. The special also manages to incorporate some clever visual effects, in spite of the different setting (it would hardly be "Sherlock," otherwise). There is some good bonding between Holmes and Watson (in spite of Holmes's best efforts to avoid it). And, given the era in which the story is set, there's a rather enjoyable and timely feminist message. And... I guess that's all I can say, except that my appetite for series 4 has been thoroughly whetted.