Sherlock Season 4 Spoilers: Special Episode Plot Details and Moriarty to Return?

BBC's smash hit drama Sherlock will return for a special Christmas episode before the premiere of its fourth season in 2016.

The most watched BBC series has maintained a two-year gap trend since the premiere of its first season in 2010.

Produced by Hartswood Films, the one episode special is rumoured to be based on the story of 'The Adventure of the Blue Carbuncle.'

The Christmas special episode was teased by Martin Freeman during an interview on Alan Carr's talk show Chatty Man.

"Mark Gatiss may beat me up, but there is an idea for this one-off special that's such a good idea," said the actor. "As I was listening to it, I thought 'we've just got to do this.' It's a fantastic, really mouth-watering idea. But I really don't know when we are going to get to do it."

The filming of the special Sherlock episode will commence in January 2015 followed by the production of its fourth season, Latin Times reported.

The special mini episode will be telecast during the Christmas holidays in 2015.

Season 4 may see the return of the criminal mastermind Moriarty who fell to his death in Season 2 from the Reichenbach Falls in Switzerland.

The final scene of Season 3 teased fans with the potential return of Moriarty in the upcoming season.

Eager fans expect Season 4 to at least clear the air about the Moriarty mystery.

Latin Times suspects that John Watson may return as a father during the show's 2016 premiere as the end of Season 3 showed a heavily pregnant Mary Morstan.

Sherlock stars Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as Doctor John Watson.