'Sherlock' season 4 news, spoilers: John and Mary prepare for parenthood; latest clue revealed in London newspaper

Sherlock (Benedict Cumberbatch) is back in Britain as the Watsons prepare for parenthood in the upcoming premiere of the hit mystery drama "Sherlock" season 4.

Titled "The Six Thatchers," the show's season 4 premiere will see Sherlock figure out where Moriarty will make his posthumous move. According to the official synopsis, John (Martin Freeman) and Sherlock take on yet another mysterious case that is baffling Scotland Yard. However, Sherlock is more interested in one seemingly unimportant detail.

They discover that an unidentified criminal is destroying images of the late Prime Minister Margaret Thatcher, which makes the detective wonder if there's a madman on the loose or if something much darker is at work. While John and Mary (Abbie Abbington) prepare to become first-time parents, the new case might lead Sherlock and John to discover a dark secret from Mary's past.

An another note, a new clue about the upcoming premiere has been found tucked in the pages of The Daily Telegraph, a daily broadsheet newspaper published in London. Aside from revealing the name of John and Mary's firstborn, it also hints what Sherlock has been up to.

"Congratulations! To John and Mary Watson on the birth of their beautiful baby daughter, Rosamund Mary Watson. From your friends, Mrs. Hudson, Molly and Sherlock, although he hasn't helped us with this at all as he's always on his phone," the announcement reads.

The new trailer might give fans an insight on why Sherlock is always on his phone. Released over the weekend, the 47-second promo clip features the first look at season 4's main villain, Culverton Smith, who played by veteran actor Toby Jones. At the end of the teaser, the enigmatic sleuth utters the words "I love you." Fans speculate that the idea of a romance for Sherlock is far from happening, so he may have said those words for a different reason.

The fourth season of "Sherlock" officially premieres on Sunday, Jan. 1, at 9 p.m. ET on PBS.