The "Sherlock" production team is not even trying to keep Andrew Scott, actor playing Jim Moriarty, a secret. Its as if they want to give its viewers a subliminal message. In fact, images of him shooting on the sets have emerged on Twitter to prove that he is really back. However, what is interesting, though, is that unlike other "Sherlock" sets, this one was free to be accessed by public.
It is important to note is that despite seeing him on the sets, it is not exactly certain that Moriarty is back on the show. The rumors about Moriarty being a part of "Sherlock" season 4 have been doing the rounds for quite some time. But whether or not is he really back, is still a mystery.
There is also a possibility that Andrew Scott was filming a flashback scene or a dream sequence. This scene may also be a part when Sherlock goes deep inside him "mind palace." In February, Steven Moffat did tease that Andrew Scott "may or may not" be a part of the show, when it returns.
According to other reports, the location shoot with Moriarty happened at St Catherine's Island where Moriarty flag was in full mast. However, Martin Freeman (Dr. Watson) and Benedict Cumberbatch (Sherlock) were not seen during the shooting.
Reports are also out indicating that the show will air in January 2017. However, other conflicting reports suggest that season 4 will air, just in time for holidays. BBC has not made any official announcement about its release date yet.
