BBC One has released the synopsis for Sherlock series 3′s final episode titled “The Last Vow” which airs in mid-January.

“In the final episode of this new series, written by Steven Moffat, a case of stolen letters leads Sherlock Holmes into a long conflict with Charles Augustus Magnussen, the Napoleon of blackmail, and the one man he truly hates,” it reads.

“But how do you tackle a foe who knows the personal weakness of every person of importance in the Western world?”

Charles Augustus Magnussen will be played by Lars Mikkelsen. We received a first look at the new villain over the summer, and at the time fans wildly speculated about his role.

Martin Freeman, who plays Watson, recently spoke about the new villain while promoting The Hobbit: The Desolation of Smaug. “[He's] like a dead man walking. He’s really scary; scary in a different way to Moriarty. Not crazy, crazy like Moriarty was, but sort of just chilling. I think you’ll like him.”

Sherlock series 3, episode 3 premieres January 12, 2014.

Before that, fans can watch episode 1 “The Empty Hearse” on New Years Day and episode 2 “The Sign of Three” on Sunday, January 5. The synopsis for both episodes have already been released – hit the respective links for the details!

… And before that, a mysterious mini episode titled “Many Happy Returns” airs on Christmas Day.

A trailer for Sherlock series 3 debuted earlier this week and depicted Watson wanting to know why – not how – Sherlock faked his death.

Edited by Brandi Delhagen