Sherlock Season 4 Release Date: The special one-off holiday episode of  BBC's Sherlock will be set in the Victorian era, according to the show's co-creator Steven Moffat confirmed. The Sherlock special episode will air December. The rest of Sherlock Season 4 will play out in 2016.

Moffat told the crowd at a South by Soutwest conference that Benedict Cumberbatch and Martin Freeman filmed the the 90 minute Sherlock special. The Sherlock Christmas episode won't be connected to season 4.

 "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. So we had this to do it - as we could hardly conceal - it's Victorian. [Co-creator Mark Gatiss] and me, we wanted to do this, but it had to be a special, it had to be separate entity on its own. It's kind of in its own little bubble," Moffat told the SXSW crowd.

Holmes and Watson, played by Benedict Cumberbatch and Martin Freeman, will go back 100 years to roughly the same time period as Sir Arthur Conan Doyle's stories.

This confirms reports that Benedict Cumberbatch and Martin Freeman, Holmes and Watson respectively, were seen shooting Sherlock in 19th century attire. Fans and reporters had been speculating whether Sherlock Holmes and Dr. Watson were attending a costume party for the special.

Indeed, it is if it is going back to the era where most of the Doyle stories were set (the 1890s) it can hardly be a piece with the Sherlock series where he is a Twitter trending icon.

Sherlock also stars Amanda Abbington (Mary), Louis Brealey (Molly Hooper) and Jonathan Aris (Anderson). Suzie Lavelle joins Sherlock season 4 as Director of Photography. Tom Hiddleston from "The Avengers" is rumored to be joining the cast as Sherlock's third brother.

The "Sherlock" special will reportedly be a one-off or standalone episode of the Sherlock Holmes series.

BBC's "Sherlock has been a critic's favorite and an audience hit. Cumberbatch has become a major star since it began in 2010.

Benedict Cumberbatch is a Emmy-winning actor who starred in The Hobbit series, "Star Trek Into Darkness," and BBC's "Sherlock." There are rumors that Marve wants him to play Stephen Strange in their upcoming Phase 3 film "Doctor Strange," according to Deadline.