New Promo Image for 'Sherlock' Christmas Special Episode Features Benedict Cumberbatch and Martin Freeman in Victorian Era

Before the new season of BBC One's wildly popular TV series "Sherlock" returns to the small screens, fans will get to be treated with a special holiday episode this December.

To amp up the excitement, the network released the first look of the Christmas segment featuring two of its beloved characters, Sherlock (Benedict Cumberbatch) and John Watson (Martin Freeman).

Both actors were seen in full period piece garb with Freeman wearing a fully-imposed mustache.

The one-off episode was previously reported to take the characters on a totally different timeline, separate from the mainstream series. Co-creator Steven Moffat clarified that fans will find Sherlock and his right hand man during the Victorian-era London.

"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 Entertainment Weekly.

Speaking about the fourth season, Moffat said that they have to persuade the two actors to return for the upcoming installment.

"[Cumberbatch and Freeman] don't need Sherlock anymore, so we have to persuade them to do it, which is fair enough," Moffat told Newsbeat. "They are very serious about it, they do love it very much. I didn't think we actually thought we'd get a fourth series out of them."