Sherlock Season 4: 9 Big Questions After 'The Lying Detective'
7. So, Who (Or What) Is Sherrinford?
After previous references to a third Holmes sibling, the show came out and said the word everyone was thinking in the last episode: Sherrinford.
The name given to Sherlock and Mycroft's other brother by William S. Baring-Gould, everyone expected this little tease to lead to the reveal of Sherrinford Holmes.
While we do get a Holmes sibling this week, what does it mean for Sherrinford? Is it another name for Eurus? Maybe, but then Mycroft is adamant that Sherrinford is "secure", which Eurus definitely isn't.
As Sherlock notes, everyone always stops when they get to three. Does this mean there is a Sherrinford Holmes out there somewhere, or does the word have a different meaning?