BBC's hit series 'Sherlock' won't officially return until spring 2017, but the upcoming Victorian-era special episode will be available to fans much sooner. However, PBS hasn't stated exactly when that will be. According to reports, the much-anticipated "Sherlock" special will air during PBS' early 2016 lineup.

TV By the Numbers published a list of premiere dates, and it also listed the series that failed to announce a premiere date. According to that list, PBS stated the Christmas special of "Sherlock" may air sometime in 2016 but hasn't set a date, which debunks reports that the special episode will air Christmas day.

Based on Sir Arthur Conan Doyle's short story "The Adventure of the Blue Carbuncle," the lengthy episode will show Sherlock Holmes and Dr. John Watson in 1890, uncovering a mystery involving a plumber with a felony record who has been accused of stealing a rare and expensive jewel.

The special will offer viewers a milder and more polite and "polished" version of Detective Sherlock Holmes, and a variation of Watson. Filmed in part at the historic Gloucester Cathedral, the dark episode is expected to be absolutely chilling.

"Ghost stories work better in a Victorian setting," said co-showrunner Steven Moffat in an interview with Entertainment Weekly  "This strand of Doyle original stories that are creepy and scary, and the chillers, we haven't done much with in the modern show. But putting it back into Victorian times, you think it's a chance to do a ghost story, really -- a creepy, scary one."

Season 4 of "Sherlock Holmes" is expected to begin filming in 2016.