'Sherlock' Season 4 Air Date, Spoilers, News & Update: BBC Revealed A Teaser For The Series, What We Know so Far!

"Sherlock" Season 4 will return and a teaser trailer has been revealed by BBC. The trailer is seen to be an animated one of Sherlock Holmes (Benedict Cumberbatch) and John Watson (Martin Freeman) in an apartment which is slowly flooded with water.

It is reported that "Sherlock" Season 4 is set to be darker than the previous seasons. The season will explore more on Mary Watson's (Amanda Abbington) past. As the upcoming season premieres, it is speculated that Moriarty (Andrew Scott) will return in the show and challenge Sherlock Holmes.

The first episode of "Sherlock" Season 4 is titled 'The Six Thatchers.' Sherlock is wondering why the images of Prime Minister Margaret Thatcher are being destroyed. He then finds out the mystery behind the act. He then wonders if a villain is out or if there is a darker mystery behind the events.

"Sherlock" Season 4 will have three episodes. The upcoming season also introduces a darker villain. Culverton Smith (Toby Jones) is yet another bad guy who tries to challenge the detective. Culverton smith is speculated to have a dark rotten soul which is depicted on his rotting teeth.

The arrival of Culverton Smith in "Sherlock" Season 4 is based from Conan Doyle's book titled 'The Adventures of the Dying Detective. ' It is not known yet if Culverton's role in the book will be followed religiously in the series.

Meanwhile, "Sherlock" Season 4 also challenges John and Mary Watson to be, first time parents. Mary is said to be pregnant once the upcoming season kicks in. John and Sherlock will be back once again to solve darker mysteries in the upcoming season of the series.

It has been a long wait for the series to be back on television. This time, "Sherlock" Season 4 is already set to return with more adventures and mysteries to solve. It is speculated that this season is going to be the last for Sherlock.

"Sherlock" Season 4 returns on January 1, 2017.