“Sherlock” is finally back, but it isn’t exactly the show fans know and love. The New Year’s Day special won’t be an episode of Season 4 (which doesn’t begin filming until April) but is instead a stand-alone installment. That allows the PBS drama to do quite a few things that it wouldn’t normally attempt. Here’s what you should know about the “Sherlock” special:

1. Victorian Era: If you really haven’t been paying attention to “Sherlock” news, you may not realize that this episode goes back in time. However, this isn’t a “Doctor Who” crossover (which will probably never happen). It’s simply an episode that shows what the drama would be like if it took place circa 1895, the era when the original Sherlock Holmes stories authored by Arthur Conan Doyle were set.

2. Different Personalities: Both Sherlock Holmes (Benedict Cumberbatch) and Dr. John Watson (Martin Freeman) will be a bit different in the “Sherlock” special. “[Sherlock has] the manners of the Victorian gentleman, which he doesn’t have in the modern version,” co-creator Steven Moffat explained at a Television Critics Association press conference, IGN reported. “So he is a lot less brattish when he’s back then. And Dr. Watson is a bit more upright. They’re the same people, seen through the prism of a different time and fitting into a different society.”

3. Defying Expectations: Although Mary Morstan (Amanda Abbington) should be sitting at home and making dinner, she’ll find a way to push back against what was typical for Victorian women. “A lot of the plot is about how women are treated in Victorian society,” co-creator Mark Gatiss (who also plays Mycroft Holmes) told TV Insider. “There’s a bit where [the men] are about to go off on an adventure and Mary says, ‘Am I just to stay here?’ And Watson says, ‘Not at all dear. We’ll be hungry later.’ Obviously, she’s going to rebel!”

Watch the “Sherlock: The Abominable Bride” trailer below:

4. The Book: The whole series is obviously based on Doyle’s novels and short stories, but this episode in particular was inspired by Doyle’s short story, “The Adventure of the Blue Carbuncle.”

5. Ghost Story: “Sherlock” writers have kept spoilers under lock and key, but they have confirmed “The Abominable Bride” is a ghost story. “So when we looked at what we were going to do, we thought going scary was what to do with a Victorian ‘Sherlock,’” Moffat told Yahoo TV. “Because that’s the thing that we don’t really get to do much in the modern one.”

6. Theatrical Release: If you love the 90-minute special enough to watch it twice, go see it on the big screen. It will head to select theaters Monday and Tuesday. Those who attend the screenings will see special features after the episode. Check out more details here.

“Sherlock: The Abominable Bride” premieres on PBS Friday at 9 p.m. EST.