It's been six long years since Benedict Cumberbatch reinvigorated Sherlock Holmes as a modern-day dandy with sexy curls and a swing coat, alongside Martin Freeman as the former army doctor with trust issues, John Watson.
Fans of the BBC drama have been waiting months for a glimpse of what awaits the dapper duo in Season 4.
Co-creator Mark Gatiss, who also stars as Sherlock's brother Mycroft, recently shared these pics under the elusive caption: "Back! #Sherlock"
But little else has been revealed about what's rumoured to be the final season of Britain's best-loved drama.
Three feature-length episodes have been scheduled to air in January 2017, though we're still waiting for an official air date and trailer...
Here's what we know so far.
Sherlock Season 3 Recap
After returning from the dead at the beginning of 2014, Sherlock went on to save London from a terrorist attack, rescue John from an untimely kidnapping and discover a murderer amid the wedding nuptials of John and Mary, where he ungallantly announced she MUST be pregnant. And that was just the first two adventures!
In the final episode, Sherlock uncovers Mary's secret past as an assassin (we still haven't recovered) that sees her shoot and nearly kill Sherlock under threat of blackmail.
Sherlock ultimately takes out the man responsible - the skin-crawlingly awful newspaper mogul Charles Augustus Magnussen (played to perfection by Lars Mikkelsen) - and avoids exile to Eastern Europe when Moriarty resurfaces with a menacing TV broadcast asking: "Did you miss me?"
Yikes! Could Moriarty be really alive and plotting a permanent end to our favourite consulting detective?
Sherlock season 4 Plot Teasers
It's no surprise the web is awash with speculation that Moriarty (or at least some past demons) will come back to haunt Sherlock and John in Season 4, which started filming on 4 April 2016.
The official BBC synopsis has only confirmed Mary's pregnancy:
"[Series 4] begins with the nation's favourite detective, the mercurial Sherlock Holmes, back once more on British soil, as Doctor Watson and his wife Mary prepare for their biggest ever challenge – becoming parents for the first time."
Co-creators Mark Gatiss and Steven Moffat have stated:
"Sherlock series 4 - here we go again! Whatever else we do, wherever we all go, all roads lead back to Baker Street - and it always feels like coming home.
"Ghosts of the past are rising in the lives of Sherlock Holmes and John Watson, bringing adventure, romance and terror in their wake. This is the story we've been telling from the beginning. A story about to reach its climax..."
Moffat has previously hinted on a befitting end to everyone’s favourite high-functioning sociopath.
He told Entertainment Weekly: "It's consequences. Chickens come home to roost. It's dark in some ways - obviously it's great fun and a Sherlock Holmes romp and all that - but there's a sense of things coming back to bite you.
"It's not a safe, sensible way to live. It's hilarious and exhilarating some days, but some days it's going to be bloody frightening."
Sherlock Season 4 Cast
Benedict Cumberbatch and Martin Freeman will be re-joined by a host of fan favourites:
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Amanda Abbington as Watson’s wife, Mary
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Rupert Graves as the clueless DI, Greg Lestrade
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Louise Brealey as love-struck pathologist Molly Hooper
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Una Stubbs as long-suffering landlady Mrs Hudson
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Mark Gatiss as Sherlock's brother, Mycroft Holmes
The real question is whether Andrew Scott will reprise his award-winning role as Sherlock’s nemesis, Moriarty.
Benedict Cumberbatch has said: "I can't wait for everyone to see season 4. But you will have to wait... though not for long... And it will be worth it."
We hope he was hinting at a final showdown!
Sherlock Season 4 Fan Theories
The fan theory gathering the most momentum is that Watson's wife, Mary Morstan, will die in childbirth. A grim prediction, but the show’s producers have warned us about a tough ride.
On a brighter note, Lestrade is tipped to make a play for Molly! An unlikely romance, but she might be keen on older men.
The first confirmed guest star is Daniel Hoffmann-Gill, recently seen as Bor in Doctor Who. His character is called Gold Teeth, but we don't know if he'll be friend or foe.
But the most exciting rumour is that man of the moment, Tom Hiddleston, will be joining the cast as – wait for it – the third Holmes brother!
Many Sherlockians have tweeted about a cryptic line from Mycroft at the end of season 3 that lends real credibility to this theory: "I'm not given to outbursts of brotherly compassion. You know what happened to the other one.”
Wow! We can only hope to see the best of British unite for a worthy climax to Sherlock and John’s life of misadventure.