Series co-creator Mark Gatiss updated all "Sherlock" fans by posting a teaser for the show's upcoming season 4.

The new image taken on the set of "Sherlock" season 4 showed a back view of Sherlock Holmes (Benedict Cumberbatch) while watching the street through the window of his 221B Baker Street apartment.

While the teaser did not reveal much about the plot of the upcoming season of BBC One's critically acclaimed detective drama, the network promised to offer a lot of new surprises and unexpected cases in season 4.

In the press release issued by the network, Gatiss said: "Whatever else we do, wherever we all go, all roads lead back to Baker Street - and it always feels like coming home."

Gatiss also said during a post interview from Den of Geek regarding "The Abominable Bride" Christmas special that season 4 will be heavier compared to the previous season.

"We did make [episodes] one and two [of season 3] actually more light-hearted because we knew he was going to shoot Magnusson, and we deliberately set out to make it like the best times for the three of them as a new team, that they would really have a great time," the series co-creator explained. "And the special really does bridge that in so many ways. Even though Mary is very proactive and a huge part, it's a sort of breathing space between 'Vow' and the next one."

This could mean that Dr. John Watson's (Martin Freeman) wife Mary (Amanda Abbington) could be in danger in the upcoming season.

The press release for the upcoming season also said that it "begins with the nation's favourite detective, the mercurial Sherlock Holmes, back once more on British soil, as Doctor Watson and his wife, Mary, prepare for their biggest ever challenge - becoming parents for the first time."

BBC One has yet to announce the official release date of "Sherlock" season 4 in the coming days.