Fans of BBC's crime-drama series have finally something good to look forward to as the next instalment of the show has been confirmed. Though Season 4 won't air before next year, fans are delighted that it is going to happen for sure as they are used to waiting for unusual durations of interval between two seasons.

Benedict Cumberbatch and Martin Freeman are all set to reprise the role of Sherlock Holmes and Doctor John Watson, respectively. Like the previous seasons, they will be facing unexpected challenges and new threats. However, stakes will be higher in Season 4.

SPOILERS AHEAD: The following part of the article contains spoilers from the yet unreleased season of "Sherlock." 

Recent rumours have stated that Season 4 is going to be significantly darker and intense than the previous seasons. As reported by Collider, at the San Diego Comic-Con 2016, Cumberbatch said that the series will be "myopically dark."

"You're talking about the end of the universe darkness. You can't see in front of you and would walk into everything dark," Cumberbatch said.

The rumours also suggest that Sherlock will be returning to London after he was forcefully exiled from the city in Season 3 finale. Once back to his old place, he will meet his partner and best friend Watson and Watson's wife, Mary Elizabeth Watson (Amanda Abbington).

Andrew Scott has also been confirmed to reprise the role of Sherlock's archenemy, Professor Jim Moriarty. Though Sherlock definitely will have to deal with the Moriarty problem, it seems there is something much bigger heading towards him.

Latest reports have confirmed that Toby Jones has been cast as an unnamed villain character. Though no details were revealed regarding Jones' character, showrunner Steven Moffat has hinted that it will be the "darkest villain" that the show will ever have. Moffat also said that the viewers will find him horrific as soon as he appears in the next season.

"Sherlock" Season 4 is scheduled to premiere next year, though the official air date has not yet been revealed.