“The Sign of Three.”
The episode will likely be based on Arthur Conan Doyle‘s novel The Sign of Four, where, among other things, John Watson meets future wife Mary Morstan. The episode is being written by Steve Thompson, who also wrote season two finale “The Reichenbach Fall.“ Prepare for feels. (Not that that doesn’t go without saying.)
Episode One: “The Empty Hearse”
Episode Two: “The Sign of Three”
Episode Three: ???
Followed by: Yet another emotionally devastating hiatus
(via: Digital Spy)