Extremis ( TV story ) Most notably , the episode revealed that was inside the vault beneath St Luke ' s University and explained how Nardole came to travel with the Twelfth Doctor after the events of " The Husbands of River Song " . The episode is also notably one of the few stories to exclude the Doctor from events occurring within the story ; as Bill , Nardole and the Doctor himself never left Earth during the story . Aside from the beginning , flashbacks with Missy and the end the whole episode was set in a virtual simulation with artificial versions of the Doctor , Bill and Nardole , with the Virtual Twelfth Doctor discovering an upcoming alien invasion , beginning a three part story arc involving the creatures responsible for the virtual simulation , the Monks . To simplify things , in a bizarre twist , the Doctor is actually watching the entire adventure with the viewers , as the events were recorded by his copy and sent to his sonic sunglasses . A similar event happened in the pre - title sequence of " Before the Flood " , where the Doctor is explaining how the bootstrap paradox works directly to the camera . Synopsis . The Vatican asks the Twelfth Doctor to investigate a mysterious book called the " Veritas " . All who read the " Veritas " immediately kill themselves . When a translation of the " Veritas " is leaked online , the Doctor must face up to the inevitable truth . . . Plot . On a distant planet , an executioner named Rafando shows the Twelfth Doctor a mechanism especially designed for killing Time Lords . He then tells him that after the execution , the body will be placed in a quantum fold chamber in case of " relapses " . Missy is then brought in , and is ordered to kneel on a dais . In the present day , sitting outside the Vault , the Doctor talks to Missy , who is inside , saying that no one can know that he ' s blind . Back on the planet , while the Vault rises from the lake , Rafando announces that the chamber is prepared . Missy begs the Doctor to let her live , while he places his hand on a lever . In order to help mask his blindness , the Doctor has modified his sonic sunglasses to give him a layout of the immediate area ( in a black and green grid - like view ) . Back outside the Vault , the Doctor gets an email titled " Extremis " on the glasses . Intrigued , he opens it . In the lecture hall , 15 men file in through the back door . Angelo greets the Doctor as Nardole enters . The Doctor is told that the Pope requested a personal audience with him . When he asks why he did not come there himself , Nardole tells him that he " is " here . The Doctor apologises saying , " The Pope doesn ' t zoom round the world in the Popemobile surprising people . Why would you do that ? " In his office , the Doctor is shown a piece of parchment that reads , " Veritas " , which literally means " The Truth " . Angelo tells him that an ancient Christian sect translated it , but committed suicide after translating it . A few months ago it was again translated , but again , all of them killed themselves after the translation . All of the bodies had been recovered , except one . In Bill ' s house , Bill has brought a girl named Penny home . Moira , thinking that she has brought a " Poor terrified man home " tells her that she has very strict rules about men , before seeing Penny , and apologising . Later Bill is pouring a cup of tea when she hears the sound of the TARDIS materializing in her bedroom . When Penny asks what it is , she says it ' s the pipes . The Pope then steps in the room and speaks rapidly in Italian before going back to the bedroom . Bill excuses herself and enters her bedroom where she sees the clergymen . Penny sees them , and freaking out , flees . Bill turns to them and says " You ' re all going to hell . " In the TARDIS , Bill angrily berates the Doctor for ruining her date , while he has Nardole explain what is happening to her . Angelo tells The Doctor that the Pope had given him an offer for confession that he had refused and that the offer still stands as he prepares a device to temporarily restore his sight . On the planet , Rafando asks if the Doctor requested a priest as a cowled figure approaches . As the figure gestures to him to approach , Rafando checks the Fatality Index and says that divine intervention is allowed for 5 minutes . The figure greets him and reads from a familiar diary . The figure pulls back his hood saying that his missus would not approve , revealing himself to be Nardole , who had been sent on River Song ' s behalf to prevent him from killing Missy , saying " Warning , I have full permission to kick your arse . " At Vatican City , Nardole and the Doctor discuss why his blindness should be kept a secret before exiting the TARDIS . Angelo shows them to the entrance to the Haereticum , a portrait of the Pope Benedict IX , which is accessed by turning a candle . Angelo orders them to stay close because the layout is supposed to confuse the uninitiated . At the planet , Rafando announces that the 5 minutes are over as Nardole pulls down his hood . Rafando orders that the sentence is now to be carried out . Missy asks the Doctor not to kill her , promising she will be good , nearly crying . In the Haereticum , Angelo shows them the cage where the " Veritas " is kept . Suddenly a light shines from a wall with a figure in the centre , before fading to nothing . Angelo goes off to check the walls for a breach , as the Doctor takes out his sonic screwdriver . They find the missing translator , named Piero in the cage . He tells them he has sent something to somewhere , before running off . A strange clawed hand then seen next to Angelo ' s head . Nardole sees that Piero had shot out the lock , as the Doctor says so much for their forbidden library to Angelo , who has vanished . In the cage , Nardole and Bill see Piero ' s laptop , which had been left behind . Checking it , they find out that he had mailed a copy of the translation to CERN . As Bill says that it is promising that one person read the " Veritas " and lived , a gunshot is heard and the Doctor ' s Sonic Sunglasses ( Which he is using to see ) register his life signs dropping . The Doctor orders them to check on Piero , as the sunglasses register life signs terminated . Nardole and Bill accuse him of trying to get rid of them . He promises not to read the book as they leave . He then opens the " Veritas " , takes out the device and attaches electrodes to his temples . In the library Nardole talks with Bill as they walk through the corridors . They find a hand holding a gun , confirming Piero ' s death . The same light is then seen again . Nardole realises that it ' s a portal to somewhere . Curious , they step through . In the cage the Doctor asks for help from Angelo as a sinister shadow is cast on a bookcase . He wonders how it will work : it will either temporarily restore his sight , or it will burn out his brain . He activates it and collapses . On the planet Missy tells the Doctor that she is his friend . When he tells her that it does not matter , she tells him she knows it does not matter saying , " I know it doesn ' t . I know I ' m going to die . I have to say it . The truth . Without hope . Without witness . Without reward . I am your friend . " The Doctor then pulls the lever , causing lightning to arc out of the spheres on the top of the 4 columns on the dais and strike Missy . Missy collapses and dies as the Doctor swears to guard her body in the Vault for a thousand years . In a 5 - sided building , Nardole , and Bill exit a broom closet , where they are seen by a woman . She asks if they have clearance for floor 3 . Asking where they are , the woman tells them they are in the Pentagon . Nardole and Bill retreat back to the closet , where they find themselves in a hub , with projectors arranged in a semicircle which project light on the wall . Stepping through the light , they find themselves in a corridor where they are greeted by Nicholas who takes them to the cafeteria , as they pass a sign that says CERN . In the cage , the Doctor opens his eyes to find that his sight has been restored . As he wonders about the impact on his regeneration cycle , the same figure seen in the light appears . He asks for its help as it buckles leather straps around him to restrain him . The Doctor notices there are more of them as the figure closes the " Veritas " and takes it while the Doctor complains . The figure tells him that what they are doing is a game . The Doctor says " Good , because I win . " and uses his sonic screwdriver to turn off the lights as the figure yells his name . The figures restore them , but the Doctor has escaped with the laptop , and with it the translation . In CERN Nicolas shows them to the cafeteria where he tell the personnel to give their last orders . He tells Bill and Nardole to look under the tables . There they find that the personnel have strapped dynamite to the table legs . In a corner the Doctor opens the laptop and begins to read the email the translator sent to CERN . Suddenly , the effects of the device begin to were off as the figures surround him . Suddenly a bright white light flares onto the screen . In CERN , when Bill asks why they are doing that , Nicholas tells them that they are saving the world . When asked how , he replies that this is not the real world . He says that the have not read the " Veritas " . Nicholas tells both of them to pick a random number and to say it at the same time . When they try , they both say the same number . Nicholas tells them that is a " Shadow Test " , and apologises to them as they escape and the building explodes . As they arrive in the hub Bill notices drops of blood on the floor . Inside Nardole realises that the projectors are actually projecting the locations . To his horror , he figures out that the world is really a holographic simulation . To see if he is right , he steps into the space between projections causing him to dissolve into pixels . Bill starts to reach out to the space , but steps through another portal . She finds herself inside the oval office . The Doctor reveals that he had listened to the translation , and that it tells of a demon , who wished to conquer the world , and to do that , he created a Shadow World that has Shadow People who think they are real . The Doctor tells her that he has deduced what it means . He tells Bill that it means that an alien race who wished to conquer Earth ran a simulation to assess the abilities of every person on Earth , especially the ones who were smart enough to realise that the world wasn ' t real . The Shadow Test works by having people say random numbers . Since computers can only generate pseudorandom numbers , two people doing that will say the same numbers . He tells her that people kill themselves to escape the simulation . Suddenly , Bill dissolves into pixels , revealing the figure behind her . The figure tells him they have killed him many times . The Doctor tells them that they have fallen into a trap they had created : their simulation is too good . He then reveals that since he is linked to the sonic sunglasses , they will have a memory print of the last few hours . He then emails the recording to the real Doctor . In the real world , the Doctor , after finishing " Extremis , " calls Bill who tells him she is doing the essay he told her to do . He tells her to call Penny that night . He then tells Missy , that she had told him she was his friend . On the planet as the executioners go to the dais to take Missy ' s body away , she wakes up and pushes them away . The Doctor reveals that he had sabotaged the execution machine into knocking Missy out instead killing her . After scaring the executioners away by tricking them into accessing his record of fatalities , the Doctor has Nardole help him move Missy to the Vault . Outside the Vault , the Doctor asks Missy how he can save his friends when he is blind , saying " How can I save them when I ' m lost to the dark ? " Story notes . Filming locations . " to be added " Home video releases . DVD releases . " to be added " Blu - ray releases . " to be added " Digital releases . " to be added "