Be it solving one puzzle after another, reading between the lines of what Mycroft has to say, or connecting with his sister and reuniting the family one violin session at a time. The episode is all about giving emotional context to everything Sherlock Holmes does. Mycroft makes the mistake of blinking for five whole minutes and the ensuing chaos gives us 'The Final Problem.' Blink and Eurus will come after the Holmes brothers. Brooke does a good job of here's-what-will-happen-if-one-of-the-Holmeses-spirals-out-of-control, reminding you of the Weeping Angels Moffat created for Doctor Who. She also pretends to be his therapist in episode two while manipulating Sherlock to go after Culverton Smith. She is the same actress we saw in episode one with whom John Watson cheats on his wife. Sherlock's sister, who we all come to know of only in episode two of this season. Characters he had deleted from his memories (and ones viewers never knew about) turn up. It is crammed with a lot of information a casual viewer may find hard to process as the episode goes on. From the days of his childhood, playing pretend pirate with his dog Redbeard, to the ominous day he has to choose between his brother Mycroft and his friend John Watson. This episode is all about Sherlock Holmes.
The season started with the timid 'The Six Thatchers,' it reached a peak with 'The Lying Detective,' and it gave an insight into why Steven Moffat and Mark Gatiss' Sherlock is the way he is with 'The Final Problem'. Three exciting weeks at the beginning of the year were all a fan could ask for. One thing is certain when it comes to the last episode of season four of Sherlock- that it has ended.