Eurus Holmes

Eurus Holmes (played by Siân Brooke) was introduced in series 4 of the show and was revealed to be Sherlock and Mycroft’s secret sister who had been institutionalised since she was a young child. She is the smartest of the three siblings and because of her intellect, became isolated and disturbed. It is revealed that she burned down the Holmes ancestral home and pushed Sherlock’s childhood friend down a well and killed him, thus leading to her being incarcerated in a secret facility called Sherringford to keep her from hurting anyone else. She eventually breaks out and ends up tormenting Sherlock, Mycroft and John in a series of elaborate mind games. The name Eurus is Greek and refers to one of the wind gods, specifically the ‘east wind.’