Katherine "Kitty" Winter Sherlock's new protege, she worked with Sherlock in London and moved with him to New York. Kitty helps Sherlock with his cases and learns his methods.
Five years before gaining the acquaintance of Sherlock, Kitty was kidnapped, raped and tortured by a male perpetrator. She now lives under an assumed identity in an attempt to escape her former reality. Kitty admits to Joan Watson that she was at a low point in her life before meeting Sherlock in London. After becoming Sherlock's protégé, essentially assuming Joan Watson's role, she follows Sherlock to New York City and resides in The Brownstone with him. Within weeks of living in the city, she gains an interest in Joan Watson; even after her surveillance of Watson was ordered to be discontinued, she persists anyway and unintentionally confronts Watson in a fight of Singlestick. Although initially having felt rivaled by Watson, Kitty begins to realize that her capabilities may be better enhanced with the assistance of Joan. Being a rape victim, she accepts Joan's recommendation of attending regular support groups, as a means of indicating her compliance with Joan. However, Kitty tells Joan that she is only doing this to fulfill her potential, just as Joan did when she was being mentored by Sherlock. Kitty accepts mentorship of both Joan and Sherlock and helps them in several cases.
However, the man who raped and imprisoned Kitty in London comes to New York( [B[S3E11], [S3E12]B]) and starts committing similar crimes IN New York. Leaving women with burned in brands like Kitty's. While in pursuit of this man, Kitty goes off track and decides to take justice into her own hands. She captures her rapist and then plans to kill him. However, Sherlock figures out what and where Kitty is and tells her that he was in a similar place at one time and it is up to her to decide what to do, she will have a friend in him regardless. At the last moment, Kitty decides to leave the rapist alive but burns his face with the nutmeg cleaner chemical she filched from an earlier crime scene which dissolves body tissues. The rapist is found alive in the warehouse by the police. Although the team is not aware who has done this to him, everyone has a strong suspicion that it is Kitty. Kitty leaves the country before the rapist wakes up to give testimony, finally declaring that she does love Sherlock.
In the last episode, Kitty appears back in New York and admits she has a son, named Archie.
- Kitty Winter is a character in the canon Sherlock Holmes short story, "The Adventure of the Illustrious Client" by Sir Arthur Conan Doyle.
- This is further alluded to in the second last episode she appears in, titled "The Illustrious Client."
Every photo of Kitty Winter on this wiki can be seen here.