BBC's "Sherlock" Season 4 is actively moving forward with the production, as some lucky fans found out when they spotted Benedict Cumberbatch shooting for the next season in London.

According to Dailymail, some onlookers said that Cumberbatch was in Sherlock's iconic dark, woollen cloak and the shooting was going on in the early hours of the morning. The scenes, which were being filmed appeared to be dramatic as well as emotional. Reports of shooting in Wales' Cardiff area have also surfaced lately.

Among several speculations doing the rounds on the internet regarding Season 4 of the series, the most prominent one concerns the return of Sherlock's arch nemesis, Moriarty (Andrew Scott). The buzz is that Moriarty is still alive. He was last seen in Season 2, where he had killed himself in the season finale titled "The Reichenbach Fall."

At the end of Season 3, a message by Moriarty ("Did you miss me?") hinted that he might be returning with the next instalment. However, whether Moriarty will actually be returning or it is just a figment of Sherlock's imagination, is yet to be seen.

Fans will have to wait until next year to find out what exactly is going to happen in the aftermath of the special episode, "The Abominable Bride." That's when Season 4 is scheduled to be released, thought the exact air date has not been announced yet.

Cuttbox has reported that another iconic villain from the original novels by Sir Arthur Conan Doyle, Culverton, will debut in Season 4 of "Sherlock." Culverton was featured in the story "The Dying Detective" and will be portrayed on screen by Toby Jones of "Captain America" fame.

Christian Today has stated that just like the previous seasons, Season 4 will also consist of three episodes.