The fourth and final season of Sherlock wraps up with one very intense theme. Family. When we first meet Sherlock and John, they were both alone. John had no close relatives and Sherlock...was well Sherlock. He didn't get attached to people, showed no sentiment and allowed reason and deduction to take the place of generosity and kindness. Then John appears and he brings together a small family made up of him and Sherlock, Mrs. Hudson, Molly Hooper, Greg Lestrade and eventually John's wife, Mary and their daughter.
Over the course of the series, Sherlock begins to shift in his opinions of the world and the people in it. The fall from St. Barts showed his absolute love for his friends, meeting Mary showed his ability to accept change and he is slowly coming around to accepting his growing celebrity status in London. However, Sherlock has many addictions and demons. And his addiction to 'the game' will become his greatest demon. It's how he controls that demon by still remaining a good man that will alter and ultimately save the lives of the family he has grown to love.
Episode 1 - The Six Thatchers
As punishment for the murder of Charles Magnussen, Sherlock was going to be sent out of the country to work on a case in Eastern Europe. However, the most unexpected happens. Moriarty shows up...all over London and Sherlock's Eastern plans are cancelled. As usual, Mycroft and the government are all scrambling as to how Moriarty is still alive and what his plans for Sherlock and John might be. Sherlock takes a slightly more calm approach to the situation and believes the best thing he can do is wait and continue his work. Dead or alive, Sherlock knows Moriarty and his terrorist group better than anyone.
Meanwhile, John and Mary welcome the birth of their daughter, Rosamund. Although, hesitant at first, Sherlock becomes attached to his new goddaughter, which only reinforces his love for the growing Watson family and his vow to always protect them. During his waiting game, Lestrade presents Sherlock to the most bizarre case. After a car is hit and explodes, officers find a one week old corpse inside.
While interviewing the family, Sherlock comes across something infinitely more strange. The family has a special dedication table to former prime minister Margaret Thatcher. Yet, something is out of the ordinary about this table that is covered with pictures and memorabilia. The family informs him that there was a plaster bust of Thatcher centered on the table, but a robbery had taken place a few days before and the bust was destroyed. Sherlock digs deeper and soon finds out that all over London there are break-ins to private homes. All these homes have one thing in common; the same replica bust of Margaret Thatcher that ends up destroyed.
This case takes an absolute shocking turn when it points to Mary Watson and her former life as a agent/spy/assassin. Prior to meeting and marrying John, Mary had been part of an elite group of agents that were sent on the most dangerous and deadly missions. After a botched assignment in Serbia, Mary was thought to be the only agent that got out alive. However, one of her former members did survive and blamed Mary for leaving him to be tortured by Serbian terrorists.
After years of trying to settle down into a normal life, Mary now realizes that her past has caught up with her. Sherlock, is not deterred by any of this and continues to keep his vow to protect the Watsons. Yet, Sherlock should know that the past cannot remain hidden forever; and when lies and secrets are revealed, the truth comes at the most devastating cost.
Episode 2 - The Lying Detective
Sherlock Holmes has found himself in many dark places, but the death of a loved one sends him literally to the darkest parts of hell. When Mary is killed, John blames Sherlock for breaking his vow to protect them. Cutting off all communication, John wants nothing more to do with his former best friend. Truly heartbroken by this, Sherlock turns to his drug addiction to cope with this triple loss (three including Rosie Watson). Both men are falling at a rapid rate, John in his grief and his refusal to accept Mary's death. Sherlock at his failure as a detective and a friend.
While on a drug high, Sherlock gets a visit from Faith Smith a client who claims that her father, wealthy philanthropist, Culverton Smith, has admitted to killing someone. However, her father made this confession to her and a group of friends while they were drugged up on a new medication and she has no idea who this person was. When Sherlock gets somewhat clearheaded he sets out to put Culverton in the news as a serial killer.
John reluctantly assists Sherlock in this bizarre investigation that has both men face to face with the menacing Smith. While at a hospital that Culverton funds, he reveals to both men his oftentimes sadistic nature and his love of the dead. Sherlock's still drug addled mind believes that he has caught him in confessing, yet is shocked when he finds out that Faith Smith never went to his flat and told him about the case at all. Furious at Sherlock's insolence, stupidity and lack of self respect, while also holding him responsible for Mary's death, John lets loose on Sherlock. All his pain, rage and fear put onto the one man he thought he could trust.
Yet, John comes across an unexpected message that was meant for Sherlock. And in this message is a case, possibly Sherlock's hardest case. "Save John Watson. Go to hell Sherlock. Pick a fight with an enemy. Do all of this for John." Sherlock has literally gone to hell and back all for the purpose to save his friend. And for John to be saved, he must save Sherlock from the murderous hands of Culverton Smith.
Episode 3 - The Final Problem
There's an East Wind coming....and that wind comes in the form of Eurus Holmes. The thought to be dead sister of Sherlock and Mycroft Holmes. Unknown by almost everybody, including Sherlock himself. For years Sherlock had no knowledge or memory of his sister who left when he was six years old. Mycroft relays to him who Eurus was, her extreme intelligence, but also her growing sinister side. When Eurus kills Sherlock's beloved dog and then proceeds to try and kill Sherlock, she is sent away to an asylum. Several years later she set fire to the asylum and was proclaimed dead. Or that that was the story that Mycroft told everyone.
According to Mycroft after Eurus killed Sherlock's dog, Redbeard, Sherlock went through intense trauma. Slowly he began to forget his sister all together and for some reason, his family never thought it important to remind him of her at all. For years, Eurus has been sheltered on an maximum security island with other lunatics. Kept away from her parents knowledge of her, Mycroft uses Euros' intelligence for government profit in spite of her insane and sadistic nature.
In
The Lying Detective, Eurus has broken free and wants to see Sherlock again. She wants to play a game, test Sherlock's intelligence and his emotional context. When Eurus is found by Mycroft and sent back to the island, Sherlock, John and Mycroft tread the dangerous North Sea to see her. Sherlock meets his sister, who has the capability to be beautiful and even charming. Yet, it doesn't take long for him to witness her ability to manipulate and use people.
Eurus is controlling the entire asylum and she sends her brothers and John through hellish challenges that will test their deduction skills and their own humanity. To save his friend, Sherlock must uncover foggy memories of a past long forgotten and in the process he saves Eurus as well. Sherlock may have won the game, but he now sees Eurus no longer as the lunatic killer, but as the lonely little sister craving her brother's love and affection. He may not have been able to save Mary, but he will work tirelessly to bring his own family back together.
And so life moves on for Sherlock and John. They rebuild their former flat, raise John and Mary's daughter, continue to care for Eurus, take refuge and love with their extended family of Mrs. Hudson, Molly and Lestrade and do what they do best. In Mary's final message to them, she deducts them both in absolute Sherlockian perfection:
There is a last refuge for the desperate, the unloved, the persecuted.
There is a final court of appeal for everyone
When life gets too strange, too impossible, too frightening, there is always one last hope.
When all else fails there are two men sitting, arguing in a scruffy flat. Like they've always been there and they always will.
The best and wisest men, I know.
My Baker Street Boys.
Sherlock Holmes and Dr. Watson.
