BBC One announced the airing of a "Sherlock" Christmas special on Jan. 1, 2016. Fans will still have to wait for the full season, though, as "The Abominable Bride" will be a standalone episode and not part of the fourth season. 

"The special is its own thing. We wouldn't have done the story we're doing, and the way we're doing it, if we didn't have this special. It's not part of the run of three episodes," creator Steven Moffat told Entertainment Weekly in an interview. 

"The Abominable Bride," set in 1895, follows Sherlock and Watson as they investigate a murder mystery. The official BBC website for the show describes the episode: 

Mrs. Ricoletti's ghost now appears to be prowling the streets with an unshakeable thirst for revenge. From fog-shrouded Limehouse to the bowels of a ruined church, Holmes, Watson and their friends must use all their cunning to combat an enemy seemingly from beyond the grave and the final, shocking truth about... the Abominable Bride!"

"Sherlock" creators Moffat and Mark Gatiss admitted that while "The Abominable Bride" is an original story, it was inspired by an original premise by Sherlock Holmes creator Sir Arthur Conan Doyle. They mentioned that there are details and references from other original stories written by him as well. 

The new episode will be broadcast in the U.S. and the U.K. on the same day. PBS will be airing the episode in the U.S. "The Abominable Bride" will also be screened in selected cinemas in the U.K. Benedict Cumberbatch and Martin Freeman will reprise their roles as Sherlock Holmes and Dr. John Watson, respectively. 

As for the regular season, it's been two years since the last episode of "Sherlock" but fans of the show will be happy to know that the fourth season is in the works. Moffat and Gatiss will be returning to write the new episodes, with shooting to start in spring next year.