Three years have passed since the viewing public has seen the perplexing character that is Sherlock Holmes (played by Benedict Cumberbatch) in the TV screen. Although a holiday special was aired in 2015, the special TV release did not really dwell on the series' story.

There are still some questions left unanswered in Sherlock's previous seasons that avid fans of the TV show are eager to unravel on the series' next upcoming season.

UNANSWERED QUESTIONS FROM SHERLOCK'S PREVIOUS SEASONS

Is Moriarty really dead?

On Sherlock's last episode of the third season entitled 'His Last Vow', the show hinted that Moriarty will be returning next season. However, it's still unclear if Moriarty is alive or someone with the same diabolical intent will be using his name.

Who is the third Holmes and will he ever be shown in the TV series?

Also in the last episode of the third season, Mycroft seem to allude to a third Holmes siblings when he said that he is "not given to outburst of brotherly compassion" and even went on saying, "remember what happened to the other one". This exchange with Sherlock seem to imply that a third Holmes will be appearing next season.

Will Watson continue to be Sherlock's wing man or has he been replaced by a dog?

With John and Mary now having a baby, it is still unclear if Watson will remain in active pursuit of investigating cases with Sherlock. The people around Sherlock are often seen as targets for his nemesis, with their growing family, it would be difficult for Sherlock to still involve John and Mary with his dangerous lifestyle.

In the teaser photo released by BBC for the upcoming fourth season of Sherlock, Cumberbatch is seen seated with a bloodhound. If the photograph is taken in an episode where the 'The Sign Of Four' story of Sir Arthur Conan Doyle (author of the Sherlock Holmes stories) is adopted, then the bloodhound will be assisting Sherlock by sniffing out clues and his name will be Toby.