The Sherlock panel at San Diego Comic-Con brought fans a trailer for the fourth season, set to air in 2017.
It was used by author William Stuart Baring-Gould in his fictional biography of Sherlock Holmes, where the eldest Holmes brother was created.
The thought of Culverton Smith teaming up with, or working for, Moriarty is exciting, as is the prospect of another Holmes brother to add to the already complicated dynamic between Sherlock and Mycroft.
However, Thatcher was used as a password in “The Hounds of Baskerville” in Sherlock season 2.