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.
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!"