Benedict Cumberbatch & Martin Freeman Begin Work On Sherlock Season 3; Season 4 Confirmed

Martin Freeman and Benedict Cumberbatch attend the UK Premiere of 'Creation', at Curzon Mayfair on September 13, 2009 -- Getty Images

"Star Trek's" Benedict Cumberbatch and "The Hobbit's" Martin Freeman are back in the "Sherlock" fold.

"#Sherlock read-through over, plenty of surprises in store for series three," BBC One, the channel behind the show in the UK (it airs on PBS in the U.S.), Tweeted on Monday, linking to THIS photo of Benedict and Martin hamming it up.

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"You are in for an absolute stonker. It's going to be a treat," Benedict said of the first episode, per Britain's Radio Times.

The episode will explain what happened when Sherlock appeared to fall (on purpose) from the top of a building, when the show returns.

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"It's a terrific episode," the actor added.

Shooting on Season 3 of the show will begin on March 18, per Deadline.

And despite both men being involved in big screen projects (they're actually co-stars in "The Hobbit" franchise as well - Benedict voices Smaug, while Martin, is Bilbo Baggins), Benedict confirmed there will be a fourth season of "Sherlock."

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"We've agreed to two more series but I could get into trouble for saying that," the actor said at the South Bank Show Awards on Tuesday, per Britain's Radio Times.

"All I know at the moment is I'm doing these three [episodes of the upcoming series] and another three," he added.

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And there could be more after that.

"It just depends on Martin and I's availability, how long we can keep it going. It depends on [co-creator Steven Moffat's] ability. I'd love to keep it going."

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