The third Holmes sibling, played by Sian Brooke, reveals herself to Watson as Sherlock’s sister, then points a gun at him and shoots. Sherlock co-creator Mark Gatiss, who plays Mycroft Holmes, said at a special Bafta screening that an extra sibling had been discussed for years.
After that dramatic ending to episode two of Sherlock, season four, fans have been left shocked by the revelation that Sherlock and Mycroft have a secret (evil) sister.
We said to casting someone who should already be a huge star who has never had the breaks.”
The final episode of Sherlock season four airs on Sunday 17 January at 8.30pm on BBC One.