'Sherlock' season 4 spoilers: a new terrifying villain is headed Holmes and Watson's way

Holmes (Benedict Cumberbatch) and Watson (Martin Freeman) will be gracing the airwaves once again with new episodes of "Sherlock" debuting in a couple of days. The dynamic duo will be trotting the streets of London trying to solve seemingly unsolvable cases intensified with the introduction of a new big baddie in town.

Fans may be used to Moriarty (Andrew Scott) lingering around, twisting everyone's head and tormenting the snazzy but talented detective, but folks behind the show think that it is time for a villain upgrade. Season 4 of the hit BBC show will introduce Culverton Smith, played by actor Toby Jones. Until now, the series is keeping details about the antagonist in the down low, but word is that the guy is scary.

"When you introduce a new villain there's more mystery about them — what's their point going to be? What are they up to? How is Sherlock is going to defeat them? You can't have the Batman vs. The Joker every week, you get depressed when the arch-enemy never seems to notice that they always lose," showrunner Steven Moffat explained to Entertainment Weekly referring to their decision to spice things up via the mysterious Smith. "It just becomes predictable. There's a whole host of less-famous ones in the stories that have never been touched," he added.

"Sherlock" is bound to start on a good note, especially with John and Mary's (Amanda Abington) newest addition. And although Sherlock would continue putting off some kind of a scorned jealous friend stance, he is genuinely happy for the growing Watsons. Unfortunately, Moffat hints that gleeful days will not last long thanks to a careless misstep from the group.

"They're all adrenaline junkies and that's bound to go wrong," the producer warned. "You can't live your life like that and have it work out forever. There will be consequences for that. You know, it's not a fairy tale. There will be a darker side for rest of the [season]," he went on to say.

If the trailer for the upcoming installment is any indication, Holmes look pretty spooked up by whatever he comes across in his newest adventures. With Smith poised to be a terrifying villain, it would be interesting how effective his planned shenanigans will be against Sherlock and his gang.

"Sherlock" season 4 premieres this Sunday, Jan. 1 on BBC One.