<Tr> <Td_colspan="7"> <P> Sherlock is contacted by the daughter of entrepreneur Culverton Smith, who she claims has confessed to a murder, but she does not know who the victim was as her father has used a drug on her that inhibits memory . Sherlock deduces that her father is a serial killer and sets out to expose him, but he has returned to narcotics use since Mary's death and unable to clearly distinguish his own thoughts from reality . He confronts and attacks Smith, and John is forced to subdue him . While recovering in the hospital, Smith appears in Sherlock's room, confesses and then tries to kill him . John bursts in just in time to save Sherlock, who reveals that his behavior up to that point was not just an elaborate ploy to expose Smith, but also fulfilling Mary's last wish for him to "Save John". Later John's therapist reveals that she is actually Sherlock's secret sister, Eurus, and has been using disguises to manipulate both Sherlock and Watson . The episode ends with Eurus firing a shot at John . </P> Title and plot elements based loosely on the Doyle short story "The Adventure of the Dying Detective". </Td> </Tr> <P> Sherlock is contacted by the daughter of entrepreneur Culverton Smith, who she claims has confessed to a murder, but she does not know who the victim was as her father has used a drug on her that inhibits memory . Sherlock deduces that her father is a serial killer and sets out to expose him, but he has returned to narcotics use since Mary's death and unable to clearly distinguish his own thoughts from reality . He confronts and attacks Smith, and John is forced to subdue him . While recovering in the hospital, Smith appears in Sherlock's room, confesses and then tries to kill him . John bursts in just in time to save Sherlock, who reveals that his behavior up to that point was not just an elaborate ploy to expose Smith, but also fulfilling Mary's last wish for him to "Save John". Later John's therapist reveals that she is actually Sherlock's secret sister, Eurus, and has been using disguises to manipulate both Sherlock and Watson . The episode ends with Eurus firing a shot at John . </P> <Tr> <Th> 13 </Th> <Td> </Td> <Td> "The Final Problem" </Td> <Td> Benjamin Caron </Td> <Td> Mark Gatiss and Steven Moffat </Td> <Td> 15 January 2017 (2017 - 01 - 15) </Td> <Td> 9.06 (UK) N / A (U.S.) </Td> </Tr> <Tr> <Td_colspan="7"> <P> Sherlock and Watson--who had been shot with a tranquilizer by Eurus--trick Mycroft into acknowledging her existence . Eurus steps up her attacks on Sherlock, culminating in the bombing of his Baker Street apartment . Sherlock, Watson and Mycroft venture forth to Sherrinford, a maximum - security psychiatric facility where Eurus is housed . Although Mycroft is skeptical at the suggestion that she has escaped, the trio discover that Eurus has compromised the staff and controls the entire Sherrinford asylum . She subjects the trio to a series of ordeals, testing their morals by forcing them to choose which of her victims live and die and ultimately forcing Sherlock to confront the memory of "Redbeard", a childhood friend whose death set in motion events that saw Eurus incarcerated . Realising that she will continue to test him until someone he cares for dies, Sherlock tries to connect with her on an emotional level, offering her the love and relationship with a brother that she never had, and Eurus stands down . Sherlock and Watson return to the Baker Street apartment, where they find another message from Mary imploring them to stay together . A time lapse montage shows them rebuilding the Baker Street flat to its original lived - in form before meeting a series of unusual clients . </P> The title matches the Doyle short story "The Adventure of the Final Problem", but the plot contains elements from the short stories "The Adventure of the Musgrave Ritual", "The Adventure of the Three Garridebs", and "The Adventure of the Gloria Scott". </Td> </Tr>

Why is there only 3 episodes of sherlock