Recently, a casting call made on Facebook specifies what Nino Firetto Casting is looking for in its young Sherlock. The post read that the actor must be between at least 3'6" and 3'9" inches tall. He must also have dark curly hair and blue eyes. The part will for a Sherlock when he was 6-years-old. The actor will be featured in non-speaking flashback scenes for the third episode of season 4.
According to fan theories, young Sherlock is an indication that season 4 will be about him and his family. However, Mark Gatiss and Steven Moffat are keeping the details of the plot tightly under wraps. Moffat called season 4 of "Sherlock" a result of consequences. "Chickens come to roost," he said.
Internet is also abuzz with speculation that the third Holmes brother, Sherrinford, will be featured in Season 4. This is expected to create strain between Sherlock and Mycroft. This could, perhaps, explain the flashback scenes that will further explain their family dynamics in the upcoming season.
However, the most sought after addition to the season 4 will be Sherlock's sister who was briefly hinted in the books by Sir Arthur Conan Doyle. Fans are already guessing that the said sister has already been featured during the show's filming as the Lady in Red.
On the sets of Sherlock, a dog was spotted too hinting at a plot that will go deeper in Sherlock's childhood. According to the books, Sherlock had a dog, Redbeard, who had to be euthanized.
"Sherlock" season 4 will air in early 2017 and will have three episodes like its previous seasons.
