The Final Problem (Sherlock)

"The Final Problem" is the third episode of the fourth series, and the series finale, of the British television series Sherlock, and the thirteenth episode overall. The episode first aired on BBC One, PBS, Channel One and 1+1 on 15 January 2017.

Plot
A young girl wakes up on an aeroplane and finds everybody asleep. Panic stricken, she picks up a mobile phone and attempts to call for help only to hear the voice of Jim Moriarty announce, "Welcome to the final problem".

After staging a break-in at his home and tricking him into revealing Eurus' existence, Mycroft Holmes reveals that, like himself and Sherlock, Eurus was also born with advanced intellectual abilities, even being described as an era-defining genius on a par with Isaac Newton. However, she also has a total lack of normal sensation and emotion.

When she kidnapped and killed Sherlock's dog, Redbeard, and set their house on fire, Sherlock's parents sent Eurus to a mental institution. But Mycroft reveals that, behind their parents' backs, he had Eurus transferred to a Government "Black site" and maximum-security facility, a "Prison within a prison", in the North Sea, Sherrinford, unknown to anyone outside very high ranking government officials and only on a need to know basis.

The whole experience had been so deeply traumatising to Sherlock that his memories of her had been “rewritten”.

Their conversation is interrupted when a quadcopter carrying a motion-activated grenade flies into Sherlock's flat. John, Sherlock, and Mycroft flee as the bomb detonates, blasting Holmes and Watson out of the windows.

Later, John and Sherlock hijack a fishing trawler to travel to Sherrinford, carrying out a diversionary plan so that Sherlock can reach Eurus' cell. The Governor of Sherringford, believing the disgruntled fisherman to be Sherlock in disguise, instructs one of his prison guards to go to Eurus’ cell. But the fisherman is actually revealed to be Mycroft and Sherlock as the prison guard.

Mycroft and John corner the prison governor, discovering that he has explicitly disobeyed Mycroft's protocol and has allowed Eurus to interact with prison staff. Using her skill to "reprogram" everyone she speaks with, Eurus has effectively ruled the prison. Meanwhile, Sherlock talks to Eurus, but after toying with him, particularly about Redbeard's death, she attacks him and knocks him unconscious (at first she made it look to Sherlock she was in a cell but later reveals she's free). The guards lock Sherlock, John, Mycroft, and the governor together in Eurus' old cell.

It’s revealed that five years prior, Mycroft granted Eurus an unsupervised five-minute interview with Moriarty as a Christmas present in exchange for detecting national security threats to Britain. During that time, Moriarty agreed to record video messages for her.

John wakes up in Eurus’ cell with Sherlock, Mycroft, and the governor.

It’s then that we hear the young girl on the aeroplane's distress call through the speakers. Sherlock tries to talk to the girl to try to help her but before he can get any more information, Eurus stops the call.

After forcing the governor to kill himself, Eurus mentally torments Sherlock, Mycroft, and Watson, forcing them into sinister games to save their lives while videos of Moriarty heckle them. Although Eurus forces Sherlock onward with the prospect of saving the girl on the aeroplane, he eventually stops the games by threatening to shoot himself when she orders him to murder either John or Mycroft. Furious, Eurus uses tranquilliser darts on the three of them.

Sherlock wakes up near the burnt-out wreckage of his family's old house. He speaks to the girl in the aeroplane to guide her in landing safely. John wakes up chained at the bottom of a well. As Eurus raises the water level in the well, John finds a human skull there. Sherlock realizes that what he thought was his dog Redbeard was his childhood friend, Victor Trevor.

Victor and Sherlock used to play pirates as children. Sherlock was “Yellowbeard” and Victor was, fittingly enough, “Redbeard.” Eurus threw him into the well and left him for dead because she felt left out of Sherlock's attention as a child.

Sherlock then figures out where Eurus is hiding by deciphering the song's real meaning that Eurus originally taunted him with when Victor went missing, which reveals that she wants him to find her. It’s also revealed that the little girl on the aeroplane has been Eurus all along. Having created the perfect metaphor in her head, “High above us, all alone in the sky, and understands everything except how to land.” The game has been a cry for help, for, whenever she closes her eyes Eurus finds herself in the plane with nowhere to land. After helping her, Sherlock sends her back to Sherrinford once he rescues John.

Mycroft explains to his and Sherlock's parents, who are angry that they had been told that Eurus was dead, that she refuses to speak to people anymore. Sherlock visits Eurus and they play the violin together instead of talking. While helping Sherlock repair his destroyed flat, John receives a video sent by Mary before she died. Sherlock and John watch as Mary explains posthumously that, whatever kind of person they may be, they will always be that of Baker Street.

Production
The setting for Sherrinford, the high-security prison, was filmed at St Catherine's Fort, St Catherine's Island off Castle Beach in Tenby, Pembrokeshire, Wales.

Musician Paul Weller made a cameo appearance, in a non-speaking role as a man lying on the floor in a Viking costume, seen near the end of the episode.

Leak and investigation
On 14 January, one day before the episode's broadcast, it was released online with Russian dialogue. Both the official Sherlock Twitter account and members of the Sherlock team acknowledged this and asked people to not share it and keep the Internet free of spoilers.

On 16 January Channel One Russia, the network holding the rights to the broadcast in Russia, issued an apology, having determined that the material had been hacked from their system. Channel One Russia announced it was conducting an investigation, while BBC, through BBC Worldwide, announced its own full-scale investigation of the leak.

Broadcast and reception
"The Final Problem" received mixed reviews from critics. Among the more positive reviews was Sean O'Grady of The Independent who gave the episode four out of five stars, stating that "Benedict Cumberbatch and Tim Freeman [sic] are their usual accomplished double act" although suggesting "Maybe Sherlock needs a little more reimagining". Meanwhile, Michael Hogan of The Daily Telegraph gave the episode five out of five stars, praising that "the dazzling script delivered laughs, excitement, and emotion .. we were left with a wiser Holmes and Watson." He also commented about the possibility of series 4 being the last series for Sherlock, stating "if this was the last-ever episode, which it surely won't be, it worked well as a sign off." Louisa Mellor of Den of Geek wrote "this was fun to watch. Fun and ultra-tense with a terrific, whooshing sense of momentum. It went like the clappers, held its breath, went like the clappers again, held its breath some more until you thought you might pass out with the dizziness." Neela Debnath of the Daily Express was also positive, writing "I can't fault the thrill ride that The Final Problem takes viewers on from the beginning to the end. Sherlock has clawed itself back from the edge." Two separate reviews in The Observer or The Guardian were positive, with one describing it as too byzantine, but "much better than it looked" and the other writing "with a visual swagger far beyond the budget – and including an eerily beautiful high-security violin duet for Sherlock and Eurus – this was a fine way to go."

However, some reviews were more critical. A third Guardian review was negative, stating Holmes had "become a parody of himself". Kaite Welsh of IndieWire scored the episode a grade of B−, writing "Steven Moffatt and Mark Gatiss wrap up their 13th episode on an elegiac note, musing on the legend that is Sherlock and Watson. It's just a shame the rest of the episode was such a mess, really". Ian Hyland of The Daily Mirror stated that he preferred it "when Holmes and Watson were just solving fairly believable mysteries. If it went back to that I'd welcome another series or two with open arms." He compared the series to the BBC series Taboo, suggesting that the latter would be a better television series for those who love Sherlock. Aja Romano of Vox also criticized the episode, praising the usual drama of Sherlock, but being critical of the fact that the episode "collapses into a muddled mess of melodrama and confusion ... there is even less logic." Romano considered the episode to be an anticlimax, saying "the episode feels like a window dressing on a completely different story."

Issues of representation within the episode were raised by some commentators. Gavia Baker-Whitelaw of The Daily Dot called the episode the "most sexist" of the TV show. She noted that Eurus, a stereotypical female villain, "ticks every box for the kind of madwoman who gets locked up in an asylum in a 19th century melodrama" and commits crimes only motivated "by a desire for male attention."