Two of the producers behind PBS's Sherlock are speaking out about the highly anticipated fourth season of the popular, revealing that the show will continue to evolve.

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Sue Vertue, Mark Gatiss and Steve Moffat, producers on Sherlock, recently spoke about going into what the new season would entail on a very broad level.

"The show has to keep evolving, it has to move on at a pace, I think," Vertue said, via Radio Times.

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"What we want to do for a fourth series is match [series three], but it's not a question of saying, 'Well we need a baddie on that scale [of Charles Augustus Magnussen].'" Gatiss said, in a special feature for the Season 3 DVD, adding, "It's about trying to find stories that have that kind of scale to them."

With Season 3, Sherlock shifted into a more character-driven form of storytelling, to the dismay of some fans. However, Moffat defends the storytelling choice.

Moffat said that episodes need to "be about something in their lives. It is not enough for it to be a mystery."

As the series grows older, the show's producers seem to be okay with continuing it forward as long as stars Benedict Cumberbatch (who plays Sherlock) and Martin Freeman (Watson) are still game.

"The idea, if we could, of finding Martin and Benedict in those chairs aged 50, sort of like the age that Holmes and Watson are usually portrayed... is sensational," Gatiss said.

Sherlock is set to return for a Christmas special in Dec. 2015 while the fourth season airs in early 2016.

Tags: Sherlock television PBS