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Extremis was the sixth episode of series 10 of Doctor Who.

Most notably, the episode revealed that Missy was inside the vault beneath St Luke's University and explained how Nardole came to travel with the 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 in the story. Bill, Nardole and the Doctor himself never left Earth during the story. Aside from a few selective scenes, 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 trilogy involving the creatures responsible for the virtual simulation, the Monks. The Doctor is actually watching the entire adventure, as the events were recorded by his copy and sent to his sonic sunglasses.


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...


On a distant planet, an executioner named Rafando shows the Twelfth Doctor a mechanism specially 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 the present, the Doctor is using his sonic sunglasses to mask his blindness, having modified them to give him a layout of the immediate area in a black and green grid-like view. While still outside the Vault, he 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 has requested a personal audience with him. When the Doctor asks why he did not come there himself, Nardole tells him that he is there.

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 afterwards. A few months ago it was again translated, but again, those who did 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 materialising in her bedroom. When Penny asks what it is, she says it's the pipes. The Pope then steps into 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 tells them that they are 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.

Back 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 five minutes. The figure greets him and reads from a familiar diary. The figure pulls back his hood, revealing himself to be Nardole, who had been sent on River Song's behalf to prevent him from killing Missy.

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.

On the planet, Rafando announces that the five minutes are over and orders that the sentence is now to be carried out. A tearful Missy asks the Doctor not to kill her, promising she will be good.

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, a man named Piero, in the cage. He tells them he has sent something to somewhere, before running off. A strange clawed hand is then seen next to Angelo's head. Nardole sees that Piero had shot out the lock, as the Doctor realises that Angelo 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 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, but he promises not to read the book. However, once they have gone, 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 the device 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, even knowing it will not change his mind; "Without hope. Without witness. Without reward. I am your friend." The Doctor then pulls the lever, activating the execution mechanism. Missy collapses and 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 onto the wall. Stepping through the light, they find themselves in a corridor where they are greeted by Nicolas who takes them to the cafeteria. 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. The figure tells him that what they are doing is a game, but the Doctor uses his sonic screwdriver to turn off the lights, allowing him to escape with the laptop and with it, the translation.

In CERN, Nicolas shows Bill and Nardole to the cafeteria where he tells 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.

At the Vatican, the Doctor opens the laptop and begins to read the email the translator sent to CERN, but the effects of the device begin to wear off and the figures from the cage surround him. Suddenly, a bright white light flares onto the screen.

In CERN, when Bill asks the reason for the dynamite, Nicolas tells them that they are saving the world. When asked how, he replies that this is not the real world. He 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. Nicolas tells them that this is a "Shadow Test", and apologises to them as they escape and the building explodes.

When they make it back to the hub, Bill notices drops of blood on the floor, and Nardole realises that the projectors are actually projecting the locations and 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 into the empty space but steps through another portal. She finds herself inside the oval office, where the Doctor is waiting. 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: an alien race who wish to conquer Earth are running a simulation to assess the abilities of every person on Earth, especially the ones who were smart enough to realise that the world isn't real. The Shadow Test works by having people say random numbers, and since computers can only generate pseudorandom numbers, two people doing that will say the same ones.

Suddenly, Bill dissolves into pixels, revealing the figure behind her, who tells the Doctor that they have killed him many times. The Doctor tells them that they have fallen into a trap they have 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 having watched the recording, calls Bill and tells her to call Penny and ask her out.

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 of 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?"



General production staff

Script department

Camera and lighting department

Art department

Costume department

Make-up and prosthetics



General post-production staff

Special and visual effects


Not every person who worked on this adventure was credited. The absence of a credit for a position doesn't necessarily mean the job wasn't required. The information above is based solely on observations of the actual end credits of the episodes as broadcast, and does not relay information from IMDB or other sources.


Time Lords[]

  • In addition to two hearts, Time Lords have three brain stems.
  • One stipulation of the Fatality Index is that a death sentence of a Time Lord must be carried out by another Time Lord. That Time Lord must also swear an oath to guard the condemned's body for 1000 years in case of relapses.
  • The Doctor worries that, because he managed to temporarily "borrow" eyesight from his future self, his future regenerations might all be blind, or he might not regenerate at all. However, since it is later revealed that it is a simulation, it has no effect on the real world.


Biological data[]

  • Cardinal Angelo is shown to be male, 52 years old, 170.0cm tall, weighs 141.1 pounds, has a resting heart rate of 71BPM and a temperature of 37.3 degrees Celsius.
  • Piero is shown to be male, 35 years old, 185.2cm tall, weighs 165.4 pounds, when in fear had a heart rate of between 129 and 133BPM and a temperature of 37.3 degrees Celsius. His heart rate dropped to 0BPM upon death.
  • The President is shown to be male, 68 years old, 169.7cm tall, weighs 163.2 pounds, in death has a heart rate of 0BPM and a temperature of 32.1 degrees Celsius. This temperature would suggest a very recent death.
  • One of the Monks has a height of 228.7cm and a weight of 94.6 pounds.
  • One member of the Pope's entourage is shown to be male, 46 years old, 176.6cm tall, weighs 183.7 pounds, has a resting heart rate of 72BPM and a temperature of 37.3 degrees Celsius.
  • A second is shown to be male, 48 years old, 156.9cm tall, weighs 168.4 pounds, has a resting heart rate of 74BPM and a temperature of 37.6 degrees Celsius.
  • A third is shown to be male, 56 years old, 179.4cm tall, weighs 187.5 pounds, has a resting heart rate of 69BPM and a temperature of 37.5 degrees Celsius.
  • A fourth is shown to be male, 39 years old, 166.2cm tall, weighs 179.0 pounds, has a resting heart rate of 77BPM and a temperature of 37.9 degrees Celsius.
  • A fifth is shown to be male, 61 years old, 162.9cm tall, weighs 174.7 pounds, has a resting heart rate of 74BPM and a temperature of 37.9 degrees Celsius.
  • A sixth is shown to be male, 67 years old, 158.2cm tall, weighs 170.5 pounds, has a resting heart rate of 68BPM and a temperature of 37.2 degrees Celsius.


  • A machine has been arranged to execute Missy.
  • The Doctor gets an email on his sonic sunglasses, which the virtual Doctor has sent from the Shadow World simulation.
  • The Doctor uses his sonic sunglasses to scan people's data, as he cannot see them. Data the Doctor can detect are gender (including male and female), age (in years), height (in centimetres), weight (in pounds), heart rate (in BPM) and temperature (in degrees Celsius).
  • He can also get a sense of the architecture around him, again using the sonic sunglasses as visual aid. However, the glasses psychically "project" a vector map of the surroundings and do not actually show him what his eyes would see if they worked.
  • The Doctor employs a reading aid with circular Gallifreyan script on it, which he hopes will temporarily restore his sight. He confirms that it's deadly.
  • Bill notes that the Haereticum has WiFi, and the Doctor says of course it does, as it's a library.
  • According to a plaque at CERN, its Large Hadron Collider, which was first tested on 10 September 2008, is the world's largest and most powerful particle accelerator. It has a diameter of 27 kilometres, and, to work, requires the magnets to be cooled at -271.3 °C, a temperature colder than outer space. To achieve this, much of the accelerator is connected to a distribution system of liquid helium, to cool the magnets, as well as to other supply services.
  • Piero has a laptop computer. He emails the translation to CERN.
  • The CERN employees all have TNT explosives wired under the canteen tables.
  • The countdown to destruction at CERN happens on a flatscreen TV.


  • CERN is the largest particle physics laboratory on the planet.
  • The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia.


  • An early Christian sect managed to translate the Veritas before all committing suicide.
  • The Veritas is older than the Catholic Church itself.
  • Suicide is understood to be a mortal sin in Catholicism, leading one to hell.
  • The Pope hopes for God to help the Doctor on his quest.
  • Pope Benedict said that the Doctor was "more in need of confession than any man breathing", but when the offer was made, the Doctor replied, "it would take too much time".
  • The Doctor says that religion is "designed to confuse the uninitiated", as Angelo says of the layout of the Haereticum.

Food and beverages[]


  • A long time ago, Nardole told the Doctor that he followed him from Darillium and that he has full permission from River Song to "kick [his] arse".
  • Nardole tells Bill that the Vatican is in Rome, which is in Italy.
  • The Haereticum contains a cage with the Veritas locked inside.
  • A total blackout has occurred at the White House. The Doctor confronts a Monk in the Oval Office.


  • Piero has a gun that he uses to kill himself.


  • Bill calls Nardole "secretly a badass", however, Nardole disputes the assessment, claiming there is "nothing secret about it".


Story notes[]


Michelle Gomez and Nick Lambon - The Aftershow - Doctor Who The Fan Show

This episode's Aftershow on Doctor Who: The Fan Show.

  • The list of names seen as recipients of emails sent by the translator before committing suicide include a number of individuals with real-life connections with the Doctor Who franchise, including Bill Pullman, who played Oswald Danes in the Torchwood Miracle Day arc - which also dealt with a scenario that changed the status quo of the entire world.
  • The typeface/font used for the display in the sonic sunglasses in this episode is the Android Insomnia font.


  • 4.16 million (UK overnight ratings)
  • 5.53 million (UK final)[1]

Filming locations[]

to be added

Production errors[]

If you'd like to talk about narrative problems with this story — like plot holes and things that seem to contradict other stories — please go to this episode's discontinuity discussion.
  • Outgoing emails on the laptop are shown, when in fact the inbox, rather than sent messages, is open on the left panel. Later, when the Doctor opens it again, the same messages appear, but now in sent.
  • The position of Nardole's hood during the scenes of Missy's execution varies between shots.
  • The reflection of a cameraman can be seen on the TV at CERN, when the camera pans in on the bomb countdown just before detonation.
  • When the Doctor turns the headphones on and is tortured with pain, his eyes are closed, but next shot they are open. Next shot, they have closed again.
  • One of the Monks in the Haereticum does not have a Monk's face. Instead, it looks like one of the skulls used in Heaven Sent repainted.


Home video releases[]

DVD and Blu-ray releases[]

This episode was released on DVD and Blu-ray as part of the Series 10 box set on 13 November 2017.

Digital releases[]

to be added

External links[]