'Sherlock' season 4 air date: Victorian special is a stand-alone episode

Martin Freeman and Benedict Cumberbatch in the official promo image for the Sherlock Christmas specialBBC

Before "Sherlock" returns for season 4, the series will air a special episode that will take the detective and his trusty right hand man, John Watson, to the beautiful Victorian era, particularly around the time Sir Arthur Conan Doyle wrote the adventures of the greatest sleuth of all time. 

That said, viewers can expect that the duo won't look the way they did in the previous seasons.

"We've got, I think you can safely say, the Sherlock Holmes and Dr. Watson of a generation – we want to see them do it in the proper outfits, just once," co-showrunner Steven Moffat revealed via Digital Spy. "That makes them the only two who've done both [period and contemporary] - apart from [Basil] Rathbone and [Nigel] Bruce, who we venerate, of course."  

Moffat also made clear, this time via Entertainment Weekly, that there won't be time-traveling involved and that the episode is a special antecedent installment to "Sherlock" season 4.

"The special is its own thing," he said. "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." 

He revealed that he along with series creator Mark Gatiss planned it do it all along but "it had to be separate entity," with its own little bubble and not part of the standard there-episode seasons of the series. 

This Victorian era-set special will air during the holidays this year. "Sherlock" season 4 will reportedly start filming in spring next year. Just recently, a report surfaced that the new season has been cancelled. Although uncorroborated, the common belief is that this rumor, which allegedly quotes Gatiss, is fabricated.