"Sherlock" is set to return this Jan. 5 with its one-shot special episode set in the Victorian era but season 4 proper is still a long way off, with production scheduled to begin in the middle of 2016. However, according to a report from Entertainment Weekly just a while back, it appears there are already plans to take the show down darker roads.

According to writer-producer Steve Moffat, the plan they have set in motion is "devastating" in nature and reduced the cast to tears when they heard what the team has in store. The series has gone dark before, particularly with episodes involving Moriarty (Andrew Scott) but it appears that this time, season 4 will go beyond that.

Writer Mark Gatiss, who also plays Mycroft Holmes, reiterated this and explained they weren't just experimenting with the show, claiming that "Sherlock" always had the tendency to go dark.

"We're going to try to take it somewhere we've never been before - and I don't mean outer space," he explained. "It will be challenging place to go. We always start with a reintroduction that builds toward a darker climax - we might just be going darker from the outset. We got a very, very good set of ideas."

It is speculated that Mary (Amanda Abbington), Watson's (Martin Freeman) pregnant wife who turned out to be an assassin, may possibly die in season 4. However, according to CrossMap , Gatiss stated that she will not be killed off in season 4.

Season 4 will have to resolve several lingering issues such as Sherlock's (Benedict Cumberbatch) return to London after he was subsequently ordered to leave the country, Moriarty's return despite being shot in the head during the season 2 finale, and to resolve any remaining mystery regarding Mary.

No release date for season 4 has been announced, but given that the series is set to begin filming next year it is speculated to premiere by late 2016 or early 2017.