Actor Benedict Cumberbatch Arrives for a Dinner to Celebrate the Work of The Royal Marsden Hosted by Britain Prince William at Windsor Castle, in Windsor
Actor Benedict Cumberbatch arrives for a dinner to celebrate the work of The Royal Marsden hosted by Britain Prince William at Windsor Castle, in Windsor, May 13, 2014. REUTERS

The production on Season 4 of "Sherlock" has yet to begin. The cast will be returning to the set of "Sherlock" in Jan. 2015 to film a one-off, special episode, which is expected to air on Dec. 25, 2015. And later next year, the production on the three episodes of "Sherlock" Season 4 is expected to begin. According to the original plan, the production was scheduled to begin in autumn this year. However, the actors' busy acting schedules have advanced the shooting schedule.

The finale of "Sherlock" Season 3 saw the return of Moriarty. His gif appeared on T.V. screens across U.K., repeating the question "Did you miss me?" According to Benedict Cumberbatch, who plays Sherlock," has said that the writers plan to explain how Moriarty returns. In an interview with MTV, the actor said that the return of Moriarty is a "very good idea." Andrew Scott, who plays Moriarty, refused to answer when BBC's Natalie Jamieson said that it must be way too early for him to have seen the script of "Sherlock" Season 4.

At the end of Season 2, Moriarty committed suicide by pulling the trigger in his mouth. Steven Moffat, co-creator of "Sherlock," has ruled out the possibility of Moriarty returning to life. Epoch Times has quoted him as saying, "He shot himself in the face. What more do you want?"

Meanwhile, Moffat had said to Entertainment Weekly (EW) that they have a plan to top Season 3. He also said that their plan for Season 4 reduced the cast members to tears. He called their plan a "devastating plan."

The plan is to take it to somewhere they have never explored before, according to Mark Gatiss, co-creator of "Sherlock." EW has quoted him as saying, "It will be challenging place to go." He also indicated that they might go darker and that they have a "very good set of ideas."

"We always start with a re-introduction that builds toward a darker climax -- we might just be going darker [from the outset]," Moffat said. "Sherlock" Season 4 is expected to premiere in 2016.