Legendary detective Sherlock Holmes will be returning to television for a single-episode special next year, 2015. While the British Broadcasting Corporation (BBC) officially announced the exciting news last month, as of yet there is no release date set for the upcoming fourth season of 'Sherlock'.

The Season 4 Christmas special is set to begin its production and filming in January of 2015, and be ready to air by December of the same year. Also, rumor has it that the 'Sherlock' Christmas special will be based on 'The Adventure of the Blue Carbuncle' storyline, however the producers have not confirmed or denied any rumors.

Fans can recall that 'Sherlock' Season 3 ended with an interesting turn of events as John Watson married Mary Morstan, and the criminal mastermind, Professor Moriarty, returned from the dead.

Based on the final episodes in the latest season, many fans speculate spoilers for the upcoming Season 4. Among the possibilities, some of the more popular ones involve a pregnancy between John Watson and Mary Morstan. Also, others say that Sherlock's third brother will make an appearance in the installment.

Beyond that, 'Sherlock' fans are calling for answers about Professor Moriarty's mysterious reappearance, and how that needs to addressed in the next season.

'Sherlock' is produced by Hartswood Films for BBC One and stars Benedict Cumberbatch as Sherlock Holmes, Martin Freeman as Holmes' sidekick Dr. John Watson, and Andrew Scott as Professor Jim Moriarty.