Benedict Cumberbatch
Pictured: Sherlock actor Benedict Cumberbatch. Will Tom Hiddleston play the third Holmes brother?REUTERS

Sherlock Season 4 will return to television on January 1, 2017 and it wouldn't be a surprise if Thor actor Tom Hiddleston is introduced as the third Sherlock brother.

The third Holmes brother was referenced in Season 3 when Mycroft reminded Sherlock about "what happened to the other one."Since then fans have been urging the showrunners to cast Hiddleston as the third Holmes brother, and their hopes were elevated when Hiddleston was photographed alongside co-creator Mark Gatiss and Sherlock star Amanda Abbington during San Diego Comic-Con.

Another clue to Hiddleston's inclusion in the mystery drama is hidden in one of the recently released promo material that shows Benedict Cumberbatch's Sherlock and Martin Freeman's Watson sitting in their Baker Street apartment, reported Radio Times.

The media outlet pointed out that the worn leather book floating in the water is a copy of Shakespeare's Henry V. Interestingly, Hiddleston acted as Henry in BBC2's Shakespeare series The Hollow Crown, which also starred Cumberbatch.

Will Sherlock bring the duo together once again? The answer to this will be revealed in less than a month's time. The first two episodes of Season 4 are titled The Six Thatchers and The Lying Detective, and it will introduce Sherlock viewers to a new villain.

"He's completely different. It's a completely different character. He's the darkest villain we've had," co-creator Steven Moffat was quoted as saying by Screen Rant. "There was always something charming and engaging about Moriarty. There was something fascinating and actually amoral, rather than immoral, about Charles Augustus Magnussen. This guy is the purest evil. Sherlock is actually appalled by him. He's the most evil villain we've had. I don't think that when you see it, you will disagree. He's horrific," he added.

Sherlock Season 4 will return to BBC on January 1.