The end of 'Sherlock' Season 3 left fans asking a lot of questions, particularly about Moriarty's death, and with Season 4 of the BBC drama not slated until the end of 2015, fans could look to Sir Arthur Conan Doyle's books for clues.

'Sherlock' co-creator Mark Gatiss suggests that might not really be of any help.

"Just because it's in the stories, doesn't mean it'll happen in the series. There's an awful lot of places to go and things to do," Gatiss said in a radio interview late last year.

"It should be clear by now that while of course, Doyle is our absolute god, we have gone quite a long way away as well. We've introduced Sherlock and Mycroft's parents"”I don't think they've ever been seen in any adaptation, so there are lots of surprises to come," Gatiss added, while also telling fans to "expect tragedy as well as adventure."

"A special, plus a new series of three episodes"”it's a record-breaking run. Of course, it's too early to say what's coming, but we're reasonably confident that the very next thing to happen to Sherlock and John is the very last thing you'd expect," 'Sherlock' writer and executive producer, for his part, said in a statement.

BBC's Twitter account suggested the same tweeting, "We're ready to unleash the most shocking and surprising series of #Sherlock yet. The only thing to expect is the unexpected."

According to several reports, production for the special episodes mentioned have already commenced in early January. Baker Street, Gloucester Cathedral, and Bristol were among some of the locations mentioned in the report.

The show's lead, Benedict Cumberbatch, has been a busy man. He is finishing his work for 'Doctor Strange', got recently married, and plays the role Alan Turing in 'Imitation Game'.

The special Christmas episodes for 'Sherlock' will air late this year, while the rest of Season 4 will premiere in 2016.