A young girl looks up as the air masks come down in the plane she's riding in. She peers out the window and then turns to see that all of the passengers are dead. When the girl can't wake her mother, she gets up and sees that the pilot and crew are also dead. The girl hears a cell phone ringing and answers it, and the caller says that he's Jim Moriarty and he welcomes her to the final problem.
Mycroft is watching an old noir film when the frames jump, showing scenes from his childhood. The words "I'm back" appear and then the film burns. Mycroft tries the door and discovers that he's locked in. A girl calls his name and the door opens, and Mycroft steps through. It slams shut behind him and he walks down the hallway, picking up a sword cane. Mycroft finds a mannequin of a girl, and tells the girl to show herself. Eurus tells him that they have all the time in the world and runs up the stairs, and Mycroft goes after her. He insists that she can't be there, and Eurus tells him that nothing is impossible. The hanging paintings' eyes start bleeding, and Mycroft insists that she couldn't have gotten out. A clown steps out and draws a sword, and Mycroft reveals his sword is also a gun and shoots at the clown. Nothing happens, and Mycroft runs down the stairs as the clown charges at him. The outside doors are locked.
Sherlock steps out and Mycroft asks him to help. His younger brother whistles, and the girl and the clown casually wait. Sherlock says that it all proves that he has a sister, Eurus, and Mycroft has secured her in an institute since an early age. He concludes that Mycroft is terrified of Eurus, and Mycroft warns Sherlock that he has no idea what he's dealing with. John steps out and says that Eurus is out, and she shot him with a tranquilizer during a therapy session. Sherlock sends the clown and girl actors off, and then leaves. John admits to Mycroft that he came up with the plan, and suggests that he go to 221B if he needs help.
The next day at 221B, Mycroft arrives but refuses to sit in the client chair. Mrs. Hudson finally tells him that he has to or they won't talk to him. He does so and Sherlock tells him to tell the truth. He admits that he can't remember Eurus, and says that Mycroft turned Eurus into a ghost story. Mycroft says that he monitored Sherlock because his demons have been waiting for a long time. When Mycroft says it's a private matter, Sherlock tells him that John stays. John asks about the age gap and if Eurus has the "deduction thing," and Mycroft says that she was described as an era-defining genius beyond Newton. He says that Sherlock is who he is because of his memory of Eurus.
Mycroft says that from an earlier age, Eurus knew things that she couldn't have known. They found her with a knife once, apparently cutting herself, but she later told Mycroft that she wanted to see how her muscles worked. At the ancestral Musgrave, Sherlock played among the fake gravestones. Sherlock starts to remember their childhood, and Eurus knocking out their dog Redbeard and hiding him away. Eurus said that the song she sung was the answer, but it made no sense. They never found Redbeard, and Eurus started calling him "Drowned Redbeard." After that, Sherlock changed and never spoke of the incident again, and eventually forgot that Eurus existed after they took her away after what happened afterward: she set the house on fire.
Continuing, Mycroft tells them that Eurus was taken to a suitable place and died there after dying in another fire that she started. He says that he told the story to his parents and admits that it's a lie, and Uncle Rudy took care of things at the secure island of Sherringford. Sherringford is a fortress designed to keep the world safe from its prisoners. Eurus has never left, and Mycroft insists that whoever they met wasn't Eurus.
A window breaks in the kitchen and Eurus starts singing from nowhere. A drone flies in with a grenade mounted on top, and lands on the floor. Mycroft explains that it has a motion sensor, and if any of them move then it will detonate and destroy the flat. Sherlock and John calculate when it will be safest for Mrs. Hudson for them to move, and Sherlock tells Mycroft to get her out. They hear Mrs. Hudson shut down her vacuum cleaner and move. John and Sherlock dive out the windows while Mycroft runs for the door. The grenade detonates, blasting the two men out the window.
Later, a ship is crossing the ocean. A voice on the radio repeats the word "Sherringford," and the captain tells his mate to ignore it. Someone walks on the cabin roof, and the two crewmen go out to find Sherlock there. John steps out and trains a gun on them. and Sherlock leaps down to capture them.
At Sherringford, the technicians detect the ship heading for them and warn it off. They say that they're heading for the rocks and are going to hit, and the technicians initiate a lockdown and call for the Governor. Alarms go off and the guards take up position. The two crewmen are tied up on the beach, and there's a message written on the sand next to them: "Tell my sister I'm here."
The Governor tries to reach Mycroft and is informed that he's in hospital and unconscious with severe injuries. When the Governor is told that Sherlock is missing, he says that Sherlock is there. The guards have found two more "crewmen": John and an older man. The Governor has them taken to a holding cell and arrives to question them. He gives his pass to a guard to put eyes on Eurus. The old man claims that John stole his boat, and the Governor says that he's well aware of who Sherlock is. "Sherlock" removes his disguise to reveal that he's Mycroft, and John says that the guard who left with the Governor's pass is Sherlock.
John tells the Governor that his security is compromised and they don't know who to trust. Mycroft tells him that if the safety and security of Eurus is compromised, the Governor won't leave Sherringford. He then checks with Sherlock via earbud, and Sherlock arrives at the cell. Mycroft warns his brother that Eurus must be limited to a minimum of human contact, and then asks if anyone has performed a psychiatric evaluation on Eurus. The Governor says that he has and figures that the tapes are in what is now his office and was the Governor's.
The guards tell Sherlock to stay back from the glass, and the monitors show her playing the violin. Sherlock goes in and Eurus hesitates briefly and then keeps playing.
Mycroft and John review the tapes, and in them Eurus says that no one tells her why she's there.
Sherlock approaches the cell glass and she speeds up playing when he gets within three feet. He quickly stps back.
On the tape, Eurus says that good and bad are fairy tales, and she says that they don't apply to her because she's too clever.
Eurus finally asks Sherlock if he brought her special hairband like she asked: the one that she made him steal from Mummy. She turns and says that it's the last thing she said to Sherlock before they took her away. Sherlock asked how she managed to get out and impersonate Faith Smith, and Eurus tells him that he can't truly see. She tells him to look at her violin, and says that it's a gift from herself. Eurus puts it in the exchange hatch, and says that she taught Sherlock how to play. Sherlock explains that he doesn't remember her at all, and Eurus realizes that he still doesn't know about Redbeard. She says that it's going to be a good day.
The Governor explains that Eurus enslaved everyone that they sent in to see her, but says that they had to try. He explains that Eurus suggested to a Dr. Taylor that he should kill his family and eventually he killed himself and his family.
Sherlock repeats his question, and Eurus tells him that he knows already. She tells him to play himself, and when he does she realizes that he's had sex.
The Governor says that Mycroft talked to Eurus and brought her a visitor on Christmas Day, and Mycroft says that he is aware of the danger. John asks what dangers, and Mycroft explains that Eurus reprograms people that talk with her.
Eurus says that she remembers everything, and John calls Sherlock. He takes out the earbud and Eurus tells him to step closer to the glass. As Sherlock approaches the glass, Eurus says that Sherlock was her favorite because she could make him laugh. Their parents stopped her because Sherlock was really screaming, and Sherlock remembers Redbeard. Eurus tells him to touch the glass.
John goes out on the balcony, and then goes in and tells Mycroft to listen to the interview tapes.
Sherlock tells Eurus that he needs her help to remember what happened to Redbeard. Eurus says that if he touches the glass then she'll tell him the truth.
John points out that the Governor is the one on the tape talking to Eurus. He asks who is in charge of the prison, and the Governor sets off an alarm. Armed guards run in and arrest John and Mycroft.
Sherlock puts his hand to the glass opposite Eurus', and she grabs it. He realizes that there's no glass there, and Eurus knocks him unconscious. She starts choking him and the guards come in, and she tells them to stop her in a minute.
As the guards lead John out, he attacks them and runs off. As he runs up to the monitor rooms, the monitors show Moriarty's face and he repeats "Miss me?' over and over. More guards arrive and knock John out.
On Christmas Day five years ago, Moriarty arrives at Sherringford by helicopter and the Governor greets him. The Governor then takes Moriarty to his office where Mycroft is waiting. Mycroft says that he's at liberty until he commits a verifiable crime, and Moriarty is a Christmas present. He explains that Eurus predicted the last three major terrorist attacks, and she requires treats. This year she wants five unsupervised minutes with Moriarty because of his interest in Sherlock's activities.
Moriarty goes to Eurus' cell and he asks what his Christmas present is. Eurus glances up at the camera Mycroft is using to monitor her, and the camera blanks out. She then says that her present to Moriarty is Redbeard.
John wakes up in a bed in Eurus' cell, the glass back in place. Sherlock, Mycroft, and the Governor are there, and a phone rings over the loudspeaker. The girl begs them for help, and then Moriarty comes in and welcomes them to the Final Problem. On the loudspeaker, the girl begs them for help, and Sherlock asks where her name is. Before he can tell her his name, the line goes dead. Eurus comes on the monitor and says that Mycroft brought her her treats, and then plays a brief video of Moriarty. She says that Moriarty recorded lots of messages for her before he died, and Sherlock asks to talk to the girl. Eurus says that the girl is trapped on a plane, and offers to reconnect Sherlock with her. However, she moves aside, revealing a woman tied to a chair. The Governor says that it's his wife, and Eurus says that she's going to shoot her in a minute She tells Sherlock to take a gun from the hatch, and tells him to choose either John or Mycroft to kill the governor. If Sherlock does it then it won't count.
The Governor begs Sherlock to do it, and Sherlock gives the gun to Mycroft. Mycroft says that he can't do it, and the Governor says that it's saving his wife. When he refuses to kill, the Governor says that he's killing his wife. Sherlock then offers the gun to John, and the Governor asks if he's married. John says that he was and she died, and the Governor asks what he would do to get Mary back. John finally takes the gun and asks the Governor if he's sure about it. The Governor says that he is, and they agree that they're both doing a good thing. As John raises the gun, the Governor turns around and waits. John pushes him to his knees and puts the gun to the Governor's head, and tells him that he should be proud. However, John finally says that he can't do it.
Grabbing the gun, the Governor says that he's sorry and shoots himself in the head. Eurus says that the governor wasn't very interesting, but the three of them were wonderful. She says that two people are dead instead of one because of John's moral code, turns, and kills the wife. Eurus then tells Sherlock to pick up the gun and to remember what happened when she tells him to use it. She says that the gun is a mercy so that he doesn’t have to kill someone with his bare hands, and Sherlock takes the gun. There's only one bullet left, and Eurus says that he'll only need one.
A door in the cell opens, and Mycroft admits that he gave Eurus treats because she's very clever. They go through the door and down a hallway into an empty conference room. The walls ae covered with dried blood, and Eurus puts the girl back on. Sherlock asks where she is, and the girl briefly describes the plane. Eurus cuts her off and says that it's time for a new game. There's an envelope on the conference table, and Eurus explains that six months ago a man named Evans was murdered from 300' away. She was the only one who solved the case, and he was shot with a rifle that is fastened to the ceiling. There are three suspects, the Garrideb brothers, and Eurus tells Sherlock to deduce which one is the killer.
Sherlock asks Mycroft for his opinion. When Mycroft refuses to be manipulated, Sherlock gives John the rifle: a buffalo gun. John takes it and Sherlock points out that one brother Nathan wears glasses. The kickback from the gun would have broken the glasses, but there's no scarring on the man's face in the photo. When Mycroft sarcastically praises John, John points out that their soldiers and have to do what needs to be done... even if his priorities got a woman killed.
Eurus wants to see some emotional reaction from Sherlock, and drops the three Garridebs men outside the window on rope. She says that she'll drop the killer into the sea, and briefly puts the girl on the line to give them motivation. Sherlock confirms that the second brother, Howard, is a lifelong alcoholic and couldn't have taken the shot. The third brother, Alex, has indications that he wore glasses until recently when he had laser surgery. Sherlock says that Alex killed Evans, and Eurus asks if he's ready to condemn the prisoner. He does so, and Eurus drops Nathan and Howard. She says that he chose the right one. When John demands to know why she killed the other two, Eurus asks if it makes a difference killing the innocent or the guilty. She drops Alex into the sea as well and tells the trio to move on. Sherlock tells John not to let Eurus distract him, and they move on.
The next room contains an empty coffin, and Eurus puts the girl back on. Sherlock has her describe an empty sea outside the plane windows and a city in the distance. Mycroft says that they have to talk her through getting the plane away from the city so it will crash in the sea. If they fail to get her to and the plane, it will crash into a city. To save the city, they have to give the girl hope. Sherlock confirms that there's no one there to help her, and Eurus cuts her off again. She tells Sherlock to start his deductions as to who will go into the coffin. Sherlock deduces that it's an unmarried woman's coffin. Mycroft finds the lid nearby and points out the plate on it, saying, "I love you." He figures that it's someone who loves Sherlock because it's all about Sherlock. Sherlock and John realize that it's Molly, and Eurus tells them that Molly's flat is rigged to explode in three minutes.
Eurus calls Molly and tells Sherlock to make Molly say that she loves him, and then she'll disarm the bomb. However, Eurus says that Sherlock isn't allowed to say that Molly's life is in danger. Molly answers the phone and they watch on a monitor as Molly makes tea instead. The call goes to voice mail, and Eurus calls again. Molly finally answers and Sherlock asks her to help him. He tells her to say, "I love you," and Molly asks why he's making fun of her. Sherlock says that it's an experiment for a case, and then says that they're friends. He promises that it's important, but Molly says that she can't say it because it's true and always has been. Molly tells him to say it first like he means it, and Eurus points out that there are thirty seconds left. Sherlock braces himself and tells Molly that he loves her, and she says it back with two seconds to spare.
Sherlock tells Eurus that he won, and Eurus says that there were no explosives in Molly's house. She tells him that he and Molly both lost because he destroyed both of their lives, and warns that the next one won't be so easy. The next door opens, and Sherlock puts the lid on the coffin... and then smashes the coffin to pieces. John picks up the gun and tells Sherlock that he has to keep it together, and after a moment Sherlock agrees.
In the next room, Eurus says that only two of them move on to the next game. She tells him that he has to choose family or friend--John or Mycroft. Mycroft tells Sherlock that John is the logical choice to shoot because what lies ahead requires brainpower, not sentiment. He reminds John that soldiers die for their country, and John agrees with him. Sherlock hesitates, and Mycrotft says that Sherlock was always the weak one and has shamed the family name. He tells him to do the right thing for once in his life, but Sherlock realizes that he's just trying to make things easy for him. Sherlock aims the gun at Mycroft and John tells him not to, but Mycroft says that it's not John's decision. Despite that, John says that he won't allow it, but Mycroft says that it's his fault because he let Moriarty meet Eurus unsupervised.
As Sherlock aims the gun at his brother, Eurus says that Moriarty thought Sherlock would make the choice. Sherlock says that it took just five minutes for Moriarty and Eurus to do all of it to them, but then puts the gun to his head and counts down from ten. Eurus tells him that he can't, saying that he doesn't know about Redbeard yet, and Eurus shoots them with tranquilizer darts.
Sherlock wakes up alone on a table in a room, with the girl speaking to him over the loudspeaker. He says that he's there, and she says that he was away for hours. Sherlock tells her to go to the front of the plane, while he discovers that the room's walls are covered with photos of a boy. John wakes up in a well and Sherlock hears him. There's no sign of Mycroft, and John realizes that he's chained to the floor. Meanwhile, Sherlock finds a dog dish in his cell with "Redbeard" on it.
The girl reaches the front of the plane and Sherlock tells her to try and find a radio. Meanwhile, John sees the sky above and realizes that he's in a well, and Sherlock shoves the wall of his cell down. Outside is Musgrave, and Eurus comes on the radio to say that Moriarty's revenge on Sherlock was her. Sherlock demands to speak to the girl, and Eurus tells him to find Redbeard first and solve his first case: the Musgrave Ritual. Meanwhile, water pours into the well, raising the water level. Sherlock finds a monitor showing John, and the girl begs Sherlock to help her as the plane leans over.
Eurus' song plays over the loudspeakers, and Sherlock says that he never found anything in it. John tells Sherlock that he found bones in the well... and Mycroft has been lying to both of them. They're not dog's bones, they're children's bones. Eurus reminds Sherlock that their father was allergic to dogs and would let Sherlock have a dog. Sherlock realizes that Redbeard was his friend victor Trevor, not a dog. Sherlock remembers playing pirates with Victor, with Victor as Redbeard. Eurus trapped trapped in the well, and since then Sherlock has always been in deep waters.
As Eurus says that she never had anyone, Sherlock remembers her playing with a toy plane. He runs out to the graveyard, remembering a stone with the name "Nemo Holmes" on it: "nemo" being Latin for "no one." Sherlock asks the girl for her help, and says that the dates on the gravestone are wrong... and the key to the cipher in the song. The message spells out that someone is lost without their brother's love, and says to seek her room.
Sherlock runs back into the house and says that the girl has to tell him her real name. Meanwhile, he enters Eurus' childhood room and finds her there on the phone. Eurus says that she's on the plane and Sherlock will save her, as she is trapped in her mind palace of the plane. Sherlock says that he can bring her home, but Eurus says that she's lost in the sky and no one can hear her. He tells her to open her eyes because he's there, and hugs her. Sherlock asks her how he can save his friend this time.
As the water rises up to John's head, someone drops a rope down the well. Sherlock pulls him up and the two of them watch as the police lead Eurus away. Lestrade says that he's confirmed that Eurus locked Mycroft in her old cell. Much to Lestrade's surprise, Sherlock addresses him by his proper first name. When one officer says that Sherlock is a great man, Lestrade tells him that Sherlock is better than that: he's a good one. Sherlock tells John that he can't bring Eurus home, and John says that he gave Eurus context.
Later, Mycroft and Sherlock tell their parents that Eurus is still alive. Mycroft says that he was trying to be kind, and they says that Eurus is their daughter no matter what. Sherlock says that Mycroft did his best, and Mycroft warns that Eurus will kill again if she has the opportunity.They demand to see her, and Mycroft warns that there's no point because she won't communicate with anyone in any way. Their mother turns to Sherlock and asks what they do now.
Sherlock goes to Sherringford and goes to Eurus' cell. He takes out his violin and plays it, but Eurus just stares off into space.
Sherlock and John go through the rubble of 221B .
Eurus finally stands up turns to Sherlock. After a moment, she takes out her violin and continues playing the song.
John receives a CD with "Miss me?" on it, and calls Sherlock over.
Sherlock and Eurus play a duet.
John plays the CD for Sherlock. It's from Mary, who says that she knows what they could become if she's gone. She knows that Sherlock is a junkie who solves crimes to get high, and John is a doctor who never came home from the war. Mary tells them that it's all about the stories and the adventures.
Sherlock and John rebuild 221B with Mrs. Hudson, and remain the court of final appeal for the desperate and the hopeless.
Mycroft and his parents watch as Sherlock and Eurus play.
Sherlock and John run out to solve another case.
Written by Gadfly on Jan 16, 2017