Note: there will be spoilers in this discussion!

Synopsis: In the final episode of this new season, long buried secrets finally catch up with the Baker Street duo. Someone has been playing a very long game indeed and Sherlock and John Watson face their greatest ever challenge. Is the game finally over?

Aired on: January 15, 2017

Note: there will be spoilers in this discussion!

Synopsis: Sherlock is asked to investigate the mysterious death of a young man, which he solves quickly but he is led into another mystery when a bust of Margaret Thatcher owned by the dead man's father is smashed. Further busts are smashed and Sherlock discovers that the mystery is linked to Mary and her past as a government agent. A figure from her past is bent on revenge in the belief that Mary betrayed him, but it is discovered that the traitor was the secretary of a British Parliamentary member. Mary is killed by the secretary when jumping in front of a bullet meant for Sherlock. John blames Sherlock for Mary's death, and their relationship is fractured.

Aired on: January 1, 2017

Note: there will be spoilers in this discussion!

Synopsis: 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 since 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 and stop him, but he is under the influence of drugs 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.

Aired on: January 8, 2017