The filming for "Sherlock" season 4 is about to start and the production team is preparing the sets. One of the show's production designers, Arwel Wyn Jones, shared snaps showing the work being done in building the sets for the new season.

There are wallpapers and all sorts of contraptions being put together inside a studio. All these should be ready by March, as official filming starts this spring in time for a January 2017 premiere of new "Sherlock" episodes.

Benedict Cumberbatch, who plays the titular character, has been a very busy man. He is currently filming "Doctor Strange," where he plays the eponymous sorcerer. He was also involved in multiple films and Broadway in the previous months.

The long wait allows fans to speculate more on what will happen in "Sherlock" season 4. The leading concern is about the possibility of Moriarty's return to the scene. In the second season, he appeared to be a goner but he made his presence felt in the last moments of the previous season.

In the third episode of "Sherlock" season 3, Moriarty's face appeared on television via a static image where he said, "Miss me?" It remains to be seen whether or not Sherlock's greatest rival will return and fans fervently hope they will see another showdown.

Series creator Steven Moffat has also been coy about Andrew Scott reprising his role. During an interview for the "Sherlock" Christmas special, he said that fans "may or may not see" the actor back as Moriarty, who appeared to have killed himself in order to discredit Sherlock.

"Sherlock" season 4 is said to premiere January next year. Moffat spent the past few months writing the script.