A trailer of the upcoming fourth season of PBS and BBC's Sherlock has been released. Upon its many twist and turns, one thing is clear: it won't be a game anymore.

According to Den of Geek, the plot has been teased by the series' executive producers Mark Gatiss and Steven Moffat. In an official statement, they state that as Sherlock Holmes (Benedict Cumberbatch) and John Watson (Martin Freeman) return to Baker Street, ghosts from their past will be making its way to the present. Gatiss and Moffat also hint that the upcoming season will bring the series to its climax.

The first two episodes have been announced through the show's Twitter account. Titled 'The Six Thatchers' and 'The Lying Detective', both have been teased in this year's San Diego Comic Con. The first episode is possibly based on Arthur Conan Doyle's 'The Adventure of Six Napoelons'. In the story, busts of the French military leader are smashed one by one, searching for a hidden pearl in one of them

The second, which could be a take on the author's 'The Adventure of the Dying Detective', will be introducing the main baddie of the season, Culverton Smith, played by Toby Jones. In the book, Holmes had to fake a deadly illness, which led Smith into admitting that he killed his own nephew. This could be something that fans would see in the next episodes.

E! also reports that a new character will be introduced in the show - with teeny tiny feet. It seems that for season four, John and Mary Watson will be having a child, which would bring a new dimension to Sherlock's good friend. There is also speculation that Mary may meet an untimely end, based on Moffat's prediction of "it all goes to hell."

Lastly, the trailer showed a side of Sherlock that is rarely seen, if ever. In the final seconds of the trailer, he is heard saying "I love you." Whether it is a trick or not, or who it is addressed to, is not clear at the moment, which should be another reason for fans watch the upcoming season.

Sherlock Season 4 will air on January 1, 2017.

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