The BBC announced Wednesday that Sherlock will return for a special and another three episodes, to begin filming in 2015.
The news was released via Twitter at 2:21 p.m. BST.
"Miss me?" #Sherlock, the hit @BBCOne drama, will return for a Special, followed by a series of three new episodes. #221back
After the briefest of exiles, #Sherlock will return to face one of his biggest mysteries yet... #221back
...why is Moriarty’s face being broadcast on every television in the land? #Sherlock #221back
Shooting on the #Sherlock special will begin in January 2015, with the series shooting later next year. #221back
We're ready to unleash the most shocking and surprising series of #Sherlock yet. The only thing is to expect is the unexpected... #221back
The Game is on - again! #Sherlock #221back
In a BBC statement, co-creator, writer, and executive producer of Sherlock Mark Gatiss said: "Series Four! At last ! It's always special to return to Sherlock but this time it's even more special as we're doing... a Special! Not only THAT, we'll then be shooting three more episodes which will take Sherlock and John Watson into deeper and darker water than ever before. The whole Sherlock team are terrifically excited to return for four new adventures. The Game is on - again!"
A few days before the announcement, Sherlock star Martin Freeman said the show would likely begin filming early next year and would return in December 2015.
BBC One's Twitter account hinted the night before that some sort of announcement was coming.
It's all gone dark... Something's coming... Or someone. Details at 2.21pm tomorrow. #221back #Sherlock
"Did you miss me?" #221back. #Sherlock http://t.co/sJXE1VeFaG
And fans soon made #221back trend worldwide.
#221back is trending worldwide.
But as new episodes have been rumoured for a long time, Twitter reaction to all of this news has been mixed.
Ahh, there's nothing like #Sherlock news to set twitter on a spiral of madness! BEAUTIFUL MADNESS!!! #221back 2015. So. Much. YES.
YES NEW EPISODES OF SHERLOCK HAVE BEEN CONFIRMED MY LIFE IS SET #221back
*waiting for @BBCOne to give us some actual news* #221back Because that was literally nothing new. Just confirming what we already knew.