Prior to premiere of BBC's crime-drama series Sherlock Season 4, the network has unveiled several teasers that will add to the excitement of the fans.

Speculations have stated that Season 4 is going to be the darkest season of Sherlock, and Benedict Cumberbath, who plays the titular character of Sherlock Holmes in the series, has also confirmed it.

Cumberbatch has said that the season will be myopically dark and much intense than the previous seasons.

"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.

In the latest promotional image, Sherlock and Watson (portrayed by Martin Freeman) can be seen, delving into much darker cases and dealing with an entirely different level of crimes.

Besides being aired on BBC, the fourth season of Sherlock might also be available on streaming service Netflix in United States around June 2017. However, it is yet to be confirmed officially whether the upcoming instalment will be available for the streaming or not.

One of the major changes that will happen in Season 4 of Sherlock is the transformation of Sherlock as he will be more socially interactive and friendly than the previous episodes and will quit his sociopath, amoral and work-obsessed life.

A new villain will be introduced in next season of Sherlock as Culverton Smith (portrayed by Toby Jones) who is considered as the darkest villain the show would have. Steven Moffat, show's co-creator, has stated that Culverton is the purest evil who manages to shock even Sherlock.

Written by Moffat and Steven Gatiss, Sherlock Season 4 will consist of three episodes and is likely to premiere in January 2017.