Spyfall (TV story)

Spyfall was the two-part opening story to series 12 of Doctor Who. It saw the Thirteenth Doctor and company team up with MI6, and re-introduced, now in a new incarnation played by Sacha Dhawan.

The Doctor's home planet Gallifrey also made a return, having not been seen since the Twelfth Doctor ran away once more in Hell Bent, with the Citadel now in ruins and the Time Lords implied dead at the Master's hand. In an ongoing story arc, the Master reveals that he has uncovered a secret about the Time Lords' history, connected to the Timeless Child. Additionally the Doctor is shown a flashback of the Remnants on Desolation and a vision of a young girl by a tall structure on a planet with a purple sky.

The two-parter also saw three classic series features making a return: the Master's Tissue Compression Eliminator, The Master's TARDIS, and Time Lord telepathic contact, which the Doctor and the Master once again use to communicate via psychic link.

The story further introduced a new wall-breaking aspect to the Time Vortex. Now, when the TARDIS breaks into Gallifrey's "time bubble", the vortex changes from its normal appearance in purple to resemble an orange ball of flaming fire.

Synopsis
The security of the entire world is at stake, so head of MI6, C, enlists the Thirteenth Doctor and her team to investigate former agent spy Daniel Barton to see if he's been turned against them. Meanwhile an alien threat that can pass through walls, even those of the TARDIS, known as the Kasaavin is wiping out spy organisations all over the planet. Can former MI6 agent "O" help them, or is he not who he claims to be?

Part One
All over the world,a sniper, a spy on a plane, and an American operative, are attacked by unknown creatures. Elsewhere, in Sheffield, Yorkshire, Ryan Sinclair plays basketball with his friends. After a missed shot, Ryan and his friend Tibo have a chat, talking about his absence due to his TARDIS travels - all of which have been blamed on different illnesses. They stop talking as they see a car parked in front of them and men in black suits standing by.

At their flat, Sonya pesters Yasmin Khan for Ryan's phone number while Yaz is packing. Hakim attempts to get the Alexa to work, and Najia is annoyed at that this is the third secondment Yaz been selected for, during her probation period. Yaz is proud, but Najia pushes on. Outside the Hallamshire Police station, Ramesh Sunder, Yaz's superior officer, does not approve, thinking he is losing his best probationer. He asks if this is undercover work but are interrupted by two men in suits requesting Yaz.

At his doctor's office, Graham O'Brien is rolling up his sleeve. His doctor notes how the time has flown since his procedure 4 years ago. He asks some routine questions, then offers condolences on his wife. He proffers a tablet for Graham to sign, which he does, and mentions that he's travelling. Graham leaves the office and sees a parked car with two men in black suits.

At M.O.T., the Thirteenth Doctor has her TARDIS up on a car lift. She's wearing dark-tinted goggles and a worker's apron. Cables and tubes are hanging down from the TARDIS's bottom. The Doctor is leaving a group voice message to her "fam" on her mobile phone, saying they are late. She hangs up and turns to see three parked cars and six men in dark grey suits, one of them approaching her. She greets them, noting they are "rocking the ominous look". The man says her friends are in the car. The Doctor goes with them.

With the companions in the backseat and the Doctor in the passenger seat, the man is driving them somewhere, guided by SatNav. Suddenly, the SatNav starts to fritz out, then a red beam shoots from it, killing the driver. The car stops in the middle of the road and the doors lock by themselves. The Doctor tries to use her sonic screwdriver, but the SatNav starts up again, noting that in 5 seconds, they will all die. The car then starts up again, driving in reverse while the Doctor tries to stop it. Red beams shoot from the SatNav. The Doctor grabs the rearview mirror and uses it to reflect a beam back to the SatNav, destroying it. The car stops just before falling off the end of the road. "C" talks over the car's speaker, and convinces the Doctor to come to MI6, in London.

The team arrives at MI6. As they climb the stairs inside, the Doctor sees the TARDIS and notes that it's arrived undamaged. Graham remarks in wonder that he's always wanted to be a spy, and Ryan banters with him that he would be a terrible spy. "C" greets them at the top of the stairs, but mistakenly addresses Graham as the Doctor. When his assistant Franklin corrects him, he notes "I read the files, the Doctor is a man." The Doctor replies that she's "had an upgrade". "C" verbally defends himself from the Doctor's and Yaz's accusations and slights, then announces that he is authorised by "every security agency around the globe" and asks for help.

While walking down the corridor, "C" tells the team that intelligence officers of all nationalities around the globe have been attacked, potentially by aliens. Arriving at a door, "C" uses a wall-mounted hand scanner to access the room and leads the team in. The passenger attacked from the Tokyo flight is present, on a hospital bed. "C" hands the Doctor a tablet, revealing the passenger's DNA has been rewritten. The Doctor mentions that this is beyond any human technology.

In his office, "C" provides Team TARDIS with three briefcases of spy equipment. "C" reveals that all of the assassinated agents were working leads related to Daniel Barton, the founder and CEO of VOR, a modern tech company that is more powerful than most governments. The Doctor says she'll need his best man, but C replies that he fired him, as alien issues are not MI6's area. Irritated, the Doctor sends the former agent a voicemail, receiving an fish image in reply. "C" warns that Barton is likely now a double- or triple-agent but an unseen sniper kills "C" before he can say more, and starts shooting at the team. The team flees to the TARDIS as Kasaavin start phasing through the office walls.

In the TARDIS, the Doctor analyses the steganography of the fish picture and determines the agent's location is the Outback. A Kasaavin starts to phase through the TARDIS door, but fails when the Doctor engages the engines. The Doctor scans the doors with her sonic screwdriver but does not get a reading. The Doctor decides the team should split up. She and Graham go to Australia to meet the former agent, while Yaz and Ryan go to VOR. Along with the spy equipment they got from "C", the Doctor also gives Yaz and Ryan a bioscanner disguised as a digital recorder.

Ryan hacks Barton's diary arrange a meeting with him. Ryan is getting panicky but Yaz calms him down. Yaz and Ryan enter VOR headquarters in San Francisco as a journalist and her photographer and are greeted inside by Barton and his assistant.

The TARDIS materialises in the Great Victoria Desert. Former MI6 agent "O" and two Australian Secret Service agents, Seesay and Browning greet the Doctor and Graham. The Doctor asks if she can look around, and proceeds into O's house without waiting for an answer. Inside, "O" and the Doctor discuss the situation, and Graham reveals "O"'s security setup. "O" states he is cautious, believing the threat will follow the Doctor to him.

In Barton's office, he confesses he only granted Yaz the interview because they are "Brits" and his mum reads their paper. Yaz uses the bioscanner discreetly while Barton electronically verifies Yaz and Ryan's false identities. With Barton's approval, Yaz proceeds with the interview, while Ryan photographs Barton and uses a spy feature of the camera to duplicate Barton's security badge. Barton's mobile phone buzzes and he cuts the interview short; before leaving, he invites Yaz and Ryan to his house for his birthday party the next day as an apology. Ryan notes that he has duplicated the ID badge, but Yaz is worried because her scan indicates Barton has only 93% human DNA.

Graham and the Doctor find O in the Australian outback. In their separate investigations, both groups encounter the same luminescent alien entities, who appear to be cooperating with Barton. In Australia, the Doctor is able to capture one of the lifeforms who reveals their intent to occupy the universe. While sneaking into VOR's headquarters with Ryan, Yaz is attacked by one such entity and transported to a strange environment. The captured alien frees itself by swapping with Yaz, leaving her in O's base. Ryan is brought to Australia and regroups with Yaz, Graham and the Doctor.

Joined by O, the four investigate Barton at his birthday party. After being confronted by the Doctor, Barton denies all accusations put to him and angrily leaves in his car. The Doctor and her companions pursue Barton on motorbikes to his private jet. Leaping aboard the jet, O reveals he is actually the Master – having been in control of Barton and the aliens, a race known as the Kasaavins, the whole time. Barton then disappears from the pilot seat, leaving a bomb in his place. The Master says to the Doctor, "One last thing. Something you should know in the seconds before you die: Everything that you think you know, is a lie.". The device detonates, shattering the nose of the plane and sending it into a nose dive. The Master then manages to escape and two of the aliens cause the Doctor to disappear from the plane, reappearing in the same environment Yaz was in earlier, leaving the others in the falling plane.

Part Two
In the aliens' dimension, the Doctor meets computer pioneer Ada Lovelace and grabs her hand when a Kasaavin appears, transporting them to an invention exhibition in 1834, where they encounter the Master. The Doctor realises the Master does not fully understand the Kasaavins when he asks her how she escaped their dimension. Ada takes her to the residence of polymath Charles Babbage, where the Doctor summons a Kasaavin via a figurine identical to the one in Barton's office, hoping to return to the 21st century. Ada grabs the Doctor's hand as she fades and they travel to Paris during World War II in 1943. They are rescued by British spy Noor Inayat Khan, with the Master posing as a Nazi officer through the use of a perception filter.

The Doctor meets the Master atop the Eiffel Tower, where the Master reveals that he had the Kasaavins kill spies to get the Doctor's attention. He also informs the Doctor that Gallifrey has been destroyed. With help from Ada and Noor, the Doctor destroys his filter and turns the Nazis on the Master, while her group uses his TARDIS to return to the present. Meanwhile, Ryan finds instructions to safely land the plane with help from a recording by the Doctor. Barton has made Graham, Yaz and Ryan persons of interest. They steal one of Barton's cars, taking them to a warehouse where they find his stern mother. Speaking at a conference, Barton reveals that the Kasaavin will rewrite humanity's DNA to utilise its storage capacity as hard drives. The Master, forced to live through the 20th century without his TARDIS, arrives in time to see the figurine device activate, only for it to fail after the Doctor meddles with the device and exposes the Master's treachery, sending the Kasaavins back to their dimension, taking the Master with them, while Barton calls for extraction.

After having set up the means for her companions to survive the plane crash, the Doctor returns Ada and Noor to their timelines and wipes herself from their memories. She visits Gallifrey's ruins, discovering a confession by the Master on how he ravaged the planet after realising their understanding of Time Lord history was a lie, mentioning the "Timeless Child". Afterwards, her companions bluntly request the Doctor explains who she is. She tells them of what she believes to be her backstory.

Cast

 * The Doctor - Jodie Whittaker
 * Graham O'Brien - Bradley Walsh
 * Yasmin Khan - Mandip Gill
 * Ryan Sinclair - Tosin Cole
 * - Sacha Dhawan
 * Daniel Barton - Lenny Henry
 * C - Stephen Fry
 * Ada Lovelace - Sylvie Briggs
 * Noor Inayat Khan - Aurora Marion
 * Charles Babbage - Mark Dexter
 * Najia Khan - Shobna Gulati
 * Hakim Khan - Ravin J Ganatra
 * Sonya Khan - Bhavnisha Parmar
 * Sniper - Melissa De Vries
 * Passenger - Sacharissa Claxton
 * Older Passenger - William Ely
 * Operative (US) - Brian Law
 * Tibo - Buom Tihngang
 * Sergeant Ramesh Sunder - Asif Khan
 * Mr Collins - Andrew Bone
 * Rendition Man - Ronan Summers
 * Ethan - Christopher McArthur
 * Seesay - Darron Meyer
 * Browning - Dominique Maher
 * Inventor - Andrew Piper
 * Airport Worker - Tom Ashley
 * Perkins - Kenneth Jay
 * Barton's Mother - Blanche Williams
 * Voice of Kasaavin - Struan Rodger

Locations

 * Kasaavin are seen attacking a Sniper in Ivory Coast in West Africa, a Passenger on a plane over the Pacific Ocean towards Tokyo and a US Operative in Moscow in Russia.
 * The US Operative reaches a safehouse.
 * Yaz and her boss Ramesh Sunder talk about her leaving her job at Hallamshire Hallamshire Police Station while still on duty.
 * Graham is a patient at Sheffield City Hospital.
 * The Doctor is making repairs on her TARDIS at M.O.T. testing bay.
 * The MI6 car, while possessed, stops in the middle of the motorway, south-east of Little Earlham.
 * The Doctor and her team are going to MI6 in London.
 * Daniel Barton was born in Bromsgrove, England, but moved to live just north of San Francisco, USA.
 * Daniel Barton's file at MI6 mentions New York, Japan, China, the Far East as well as Austin, Texas.
 * The Doctor and team go to the Great Victoria Desert in Australia.
 * The Kasaavin have their own reality that looks like an underwater location, without water, filled with electricity-charged kelp. Yaz likens it to nothingness and nowhere.
 * The Doctor parks the TARDIS in the Vallis Estate vineyard.
 * The TARDIS Team once took a trip to the Great Kalisperon Bike-Off.
 * Barton has his own personal airport.
 * The Master says that MI6 has a "surprisingly good" staff canteen.
 * The Doctor says the Kasaavin realm cannot be a planet nor a void and wonders if it's a separate dimension beyond her universe.
 * Ada's Kasaavin takes the Doctor and her to the Royal Gallery of Practical Science at the Royal Adelaide Gallery in the 19th century in the middle of an auction of inventions.
 * The Doctor's companions land in Essex, Britain.
 * The Doctor tells Ada she's a traveller in Space and Time.
 * An advertising screen shows an ad with mountains.
 * The Doctor, Ada and Charles go to his house.
 * The Doctor discovers the concept Multiple Earths are actually different time periods.
 * Graham, Ryan and Yaz hide at a building site.
 * The Doctor and Ada travel to a bombsite in Paris in 1943 during the World War II.
 * Noor takes the Doctor and Ada to her house.
 * The Master has his base in an underground bunker.
 * The Doctor and the Master meets atop the Tour Eiffel.
 * The Doctor and the Master talk about Jodrell Bank.
 * The Master likens the Kasaavin to Russia, but bigger.
 * Daniel Barton holds a presentation in an auditorium.
 * The Doctor travelled to mid-2019 to put a fail-safe into the Silver Lady.
 * Gallifrey has been burned and ravaged inside its bubble universe.

TARDIS

 * The Doctor says her repairs are "draining the water slides, the boating lakes and the rainforest floor".
 * The TARDIS has a lower substrata, wardrobe hall and karaoke buses.
 * The Master disguised his TARDIS as "O"'s house.
 * The Doctor says she and Yaz are fizzing with artron energy.

Individuals

 * An older passenger talks to another passenger who mentions her sister.
 * The US Operative calls for an extraction team.
 * Ryan misses a basketball-shot due to his dyspraxia.
 * Yaz has been chosen for secondment at her job.
 * Yaz is a probationer at her job.
 * Mr. Collins is Grahams doctor.
 * Mr. Collins offers his condolences on Grace O'Brien's death.
 * Franklin informs C about the Doctor's new change.
 * The Doctor has a file at MI6.
 * The Doctor once lived in the Outback for 123 years.
 * An agent approaches the Doctor and asks her to come with them.
 * The plane passenger spy managed to make contact with her informant.
 * Barton has a handler in New York.
 * Nick Murry once wrote an article on Daniel Barton.
 * C's office has the Flag of General Davis hanging in it.
 * The Doctor once took a correspondence class.
 * Daniel Barton's aide greets "Logan" and "Sofia".
 * Barton fired "half" (actually just two) of the VOR PR-team due to a mix-up.
 * "" has his own security agents, Seesay and Browning.
 * Barton finds Ben Davis, Billie, M Porter and Ellie Simmons among Sofia Afzal and Logan Jackson.
 * Yaz mentions her title of PC Khan.
 * "O" likens the Kasaavin's light intensity to it taking a suicide pill.
 * "O" has exiled himself away from everything.
 * "O" briefly met the Doctor once when she was a man.
 * "O" has a whole shelf of information about the Doctor, however with a lot of inconsistencies.
 * "O" says they should be asking who the spymaster is.
 * Barton's birthday party has a receptionist and security guards. One of them is named Anya.
 * "O" worked as an analyst in MI6.
 * The Vallis Estate roulette croupier informs Ryan that he won a round.
 * Daniel Barton has his own personal driver.
 * The real "O" was shrunk by the Master via tissue compression and placed in a matchbox.
 * The Doctor wonders what the energy bolts in the Kasaavin realm are and suggests pathways, signals and synapses.
 * The Doctor meets Ada Lovelace from 1834.
 * Ryan mentions he can't ride a bike but can fly a plane.
 * The Doctor, when questioned about her apparition out of nowhere, claims herself to be "The Marvelous Apparating Man/Lady".
 * The Doctor meets Charles Babbage.
 * The airport worker at the Essex airport tells Barton that he would have to do a lot of explaining to the Civil Aviation Authority.
 * The Master mentions his two hearts.
 * The Doctor mentions Lord Byron and Annabella Milbanke and tells Ada she might meet a nice Earl.
 * The Doctor and Ada meet Noor Inayat Khan.
 * The Doctor, Ada and Noor hide from German soldiers.
 * Barton kills his mother.
 * Noor says she doesn't have any guns or cyanide pills and that she's a pacifist.
 * Graham threatens to perform the soft-shoe shuffle.
 * Daniel Barton's goons are rendered useless.
 * The Doctor and the Master use a psychic link.
 * The Doctor mentions that the Master is not Aryan and he in turn says he uses a tiny Teutonic psychic perception filter.
 * The Master says the Kasaavin were sleeper agents that had always been present on Earth.
 * The Master says his plan is maximum carnage.
 * The Doctor says Noor is Blighty's best radio operator.
 * The Doctor lock-picks the Master's TARDIS.
 * The Kasaavin place agents on everyone important to the development of computers through history starting with Ada Lovelace, then on to Alan Turing, Steve Jobs, Grace Hopper...
 * The Doctor assures Noor that fascists never win.
 * The Master mentions the Timeless Child in a hologram message.
 * The Doctor mentions she was born on the planet Gallifrey in the constellation of Kasterborous, that she's a Time Lord, that she can regenerate her body, that she stole her TARDIS and ran away and been travelling ever since, and that the Master was one of her oldest friends and they went very different ways.

Illness and injuries

 * Ryan excuses his absence with appendicitis.
 * Ryan excuses his absence with hernia.
 * Ryan excuses his absence with detached retina.
 * Mr. Collins asks Graham about weight fluctuations, tiredness, muscular aches and pains.
 * Yaz asks if the plane spy is in a coma.
 * When the Doctor exposes Daniel Barton, he tells her to take her medication and seek psychiatric help.
 * Ada's body is paralysed while she is in the Kasaavin's realm.

Foods and beverages

 * The secret spy plane-passenger has secret encrypted code hidden in the cap of a tube of Pearl & Diamond toothpaste.
 * "O" makes a cup of tea.
 * The Doctor thinks she made iced tea.
 * Barton knows how many stamps the companions need for a free coffee.
 * Charles Babbage drinks a glass of brandy.
 * Graham calls Ryan and Yasmin donuts.

Technology

 * A woman spy is using a sniper against an enemy-line Jeep.
 * An aeroplane is flying towards its destination as the tannoy informs the passengers to get ready.
 * The spy passenger wears spy glasses with in-built camera lenses.
 * Hakim tries and fails to use Alexa.
 * The Doctor calls her team via a group message.
 * Graham calls the MI6 cars the "worst Uber ever".
 * The MI6 SatNav attacks the Doctor and her team.
 * MI6 uses hand scanners to enter rooms at the building.
 * The plane spy has had her DNA rewritten.
 * The spy equipment C offers team TARDIS includes anaesthetic darts, laser shoe guns, an infrared ID duplicator, a calendar hacker, lock-breakers, rocket-launcher cufflinks, a retinal ID decoder, tongue-immobiliser chewing gum and a bio-scanner disguised as a digital recorder.
 * VOR is a search engine with web apps, social, global mapping, advertising, scientific and medical research, robotics, data polling and human analytics.
 * The Doctor contacts using an iPhone, through WhatsApp.
 * "O" encrypted his location using steganography.
 * MI6's spy camera has a Pentax flash.
 * In "O"'s house there's an excerpt saying that a droning alarm sparks UFO fears.
 * "O"'s house has movement sensors.
 * "O"'s house has an energy barrier around it which can be re-routed to specific areas inside it.
 * VOR has CCTV all over the company.
 * VOR seeps into every corner of modern technology: Leisure, commercial, military, face-tagging, biodata, robotics.
 * The Doctor uses a projector.
 * Daniel Barton leaves his party in a blue Bentley.
 * Barton has a Desert Eagle gun.
 * Barton talks with Air Traffic Control in Lonsdale tower to request clearance for plane take off. Air traffic control then "cleared to Hawkston radar vectors to Skaggs Island, then as filed. Squawk 4634."
 * The Master has installed a cock-pit bomb in the VOR plane.
 * The Master teleports off the plane.
 * The Doctor has installed a plane pamphlet in Barton's plane entitled How To Land A Plane Without A Cockpit.
 * Ryan's phone gains an app called Piloting Made Easy.
 * Barton's plane experience a power surge.
 * At the 19th century auction a variety of items are being shown:
 * Perkins is showing off his steam gun.
 * A man is showing off a mouse inside his diving bell.
 * A man is showing off his magneto.
 * A man is showing off his grenade.
 * Barton has Graham, Ryan and Yaz's telephone numbers, Emails and GPS.
 * The Doctor takes a look at Charles Babbage's Difference engine and the Silver Lady.
 * Noor has a wireless radio transmitter issued by the British Special Operations Executive.
 * Yaz talks to Sonya Khan about her and their mom and dad from a telephone box via the number 01632 960470.
 * The Master used a Mandraffian laser rifle to assassinate C.
 * The Doctor uses a laminator to create the plane pamphlet.
 * The Master has put a geo-activated hologram message in the Doctor's TARDIS.

Games and sports

 * Ryan, Tibo and their friends play basketball.
 * Daniel Barton's birthday party has roulette, Poker, Blackjack, dice etc.
 * Barton says his birthday party is Casino-theme and not Whodunnit.
 * "O" was a champion sprinter. The Master is not good at sprinting.

Companies and organisations

 * The spy chewing gum is disguised as Bingleys Fresh Mint.
 * Daniel Barton owns VOR.
 * Barton's file mentions the CIA.
 * The Doctor mentions GCHQ.
 * C mentions UNIT and Torchwood.
 * "O" is protected by the Australian Secret Service.
 * Ryan's ID duplicator is disguised as an Olympus camera.
 * Ryan, Graham and Yaz pass a W H Smith store.
 * Ryan, Graham and Yaz pass a NatWest bank.
 * Ryan has a Samsung phone.
 * Ryan, Graham and Yaz are classified as "Wanted", with anyone knowing about their whereabouts encouraged to contact local police or call Crime Prevention on 0800 999 999.
 * Barton doesn't like using Facebook.

Popular culture

 * Hakim asks Alexa to play Rubber Soul.
 * Ryan decides that his spy name will be "Logan", but starts panicking upon realising he looks "nothing like Hugh Jackman".
 * When describing his collection, "" says that it includes a "complete set of 'Fortean Times' in mint condition".
 * "O" asks if Graham is there just for the "running commentary".
 * During the lead-up to his real identity, "O" states that his house flying outside the plane is "[a] bit Wicked Witch of the West".

Story notes

 * This was the first multi-part television story to be given one overarching title since 2009-10's The End of Time, and only the second such story in the BBC Wales era.
 * Incidentally, both stories aired in part on New Year's Day, and both featured the Master.
 * Part One of Spyfall was, in fact, broadcast on the 10th anniversary of 1 January 2010's The End of Time: Part Two. Each aired on the first day of their respective decade, according to one outlook on the bounds of such a measurement, which this wiki follows.
 * This is the first story in the show's history to have its parts air four days apart rather than a whole week. 1 January and 5 January 2020, respectively.
 * It is also the first time two Doctor Who episodes have been shown the same week since The Twin Dilemma Parts Three and Four in March 1985.
 * The first part of this story was dedicated to the memory of the "Masterful" Terrance Dicks. Dicks was script editor for 's debut story, Terror of the Autons.
 * This story's title is a play on the 2012 James Bond film Skyfall.
 * According to one news source, the story also pays homage to Casino Royale, the first novel in the Bond series, which was centred on gambling and aristocracy.
 * The concept of MI6 members being known by a single letter, namely "C" and "O", may also be in reference to a similar feature ("M" and "Q") seen throughout the James Bond franchise, introduced in the original novels by Ian Fleming.
 * Part One marks the first episode since Twice Upon a Time to include a "cold opening". Part Two, however used a re-cap of Part One rather than a new scene. "Cold openings" would be a fluctuating on/off feature in Series 12.
 * Part Two is the first "follow-up" episode of Doctor Who to feature a re-cap with an opening voiceover: "Previously on Doctor Who...", read by Thirteenth Doctor actor Jodie Whittaker. The prior norm for Doctor Who, and indeed its televised spin-offs, was the use of an on-screen caption which typically read "Previously".
 * This formula was previously used by Big Finish Productions in the recap to Neverland which opened Zagreus. In that case, the voiceover was provided by Don Warrington, who voiced Rassilon in both stories.
 * Similar to The Return of Doctor Mysterio and its predecessor, Part One of this story aired exactly one year after the preceding episode.
 * This story marked the first time a villain has been capable of physically breaking through the sealed TARDIS doors.
 * This is the first multi-part television story to have more than one credited director since Planet of Giants in 1964.
 * Part Two was originally going to feature a scene in which Noor Inayat Khan is captured as an enemy spy and executed by the Nazis. It ended up being cut.

Ratings

 * Part One - 4.88 million (BBC overnight)
 * Part Two - 4.65 million (BBC overnight)
 * Part One - 6.89 million (BBC overall)
 * Part Two - 6.07 million (BBC overall)

Filming locations

 * South Africa - Australian outback
 * Wales
 * Cardiff Central Police Station - Hallamshire Police HQ
 * Swansea Guildhall, Swansea - C's office, MI6

Production errors
to be added

Continuity

 * A doctor offers Graham his condolences regarding Grace O'Brien's death. (TV: The Woman Who Fell to Earth)
 * It has been four years since Graham's operation. Previously, in September 2018, he told the Doctor that he had been in remission for cancer for the past three years. (TV: The Woman Who Fell to Earth)
 * The Doctor's life is once again threatened by a SatNav device controlled by a power intent on killing target passengers. In her tenth incarnation, the Doctor narrowly escaped from an ATMOS-controlled UNIT vehicle which was about to plunge him and Jenkins to their "final destination". (TV: The Sontaran Stratagem)
 * When C dismisses the possibility of alien life, the Doctor tells him to ask GCHQ, referring to the Dalek attack of New Year's Day 2019. (TV: Resolution)
 * The Doctor remarks in surprise at an entity's abilty to enter the TARDIS given its high security. (TV: Rose, The Parting of the Ways, Journey's End)
 * The Doctor notes that both UNIT (TV: Resolution, PROSE: Lucy Wilson and the Bledoe Cadets) and Torchwood (TV: Doomsday, Children of Earth: Day One, AUDIO: Thoughts and Prayers) are "gone".
 * The Master, while still under the guise of O, refers to the Doctor as having once been a man. (TV: An Unearthly Child, Twice Upon a Time, et al.) Graham recalls the Doctor having made this claim, which he believed to be a joke. (TV: The Woman Who Fell to Earth)
 * Ada's involvement with the Star Chamber and Faction Paradox in the Clockwork Ouroboros affair were detailed in The Book of the War. (PROSE: The Book of the War)
 * Graham is mistaken as the Doctor, (PROSE: The Good Doctor) and the Doctor herself is immediately dismissed, in favour of Graham, on account of her gender. (TV: The Witchfinders)
 * The Doctor refers to her regeneration to female form as an "upgrade", much as once did. (TV: The Witch's Familiar)
 * The Master once again spends an extensive amount of time masquerading as someone else in order to carry out a long-term plan. (TV: The Sound of Drums, World Enough and Time)
 * The Master uses his Tissue Compression Eliminator. (TV: Terror of the Autons,  The Deadly Assassin, Logopolis, Time Flight, et al.)
 * The Master claims to be the Doctor's "best enemy". Within the Death Zone, the Third Doctor previously identified as such to Sarah Jane Smith. (TV: The Five Doctors)
 * The Master mentions how the Time Lords view him and the Doctor as renegades. (TV: The War Games, Terror of the Autons, The Deadly Assassin, The Five Doctors, The End of Time, Heaven Sent, Hell Bent)
 * Ryan says he is still unable to ride a bicycle. (TV: The Woman Who Fell to Earth)
 * The Doctor once again forgets to alter her language to account for her new gender. (TV: The Ghost Monument)
 * The Fourth Doctor previously met Ada Lovelace at a later point in her life. (AUDIO: The Enchantress of Numbers)
 * Graham recalls the Doctor mentioning regeneration on the day they first met. (TV: The Woman Who Fell to Earth)
 * The Doctor taps a morse code of four beats, the heartbeat of a Time Lord, which she notes she and the Master have a personal connection to. (TV: Utopia/The Sound of Drums/Last of the Time Lords, The End of Time)
 * The Doctor steals the Master's TARDIS, mirroring how the Master once did likewise with the Doctor's TARDIS. (TV: Utopia)
 * The Doctor and the Master use Time Lord telepathic contact (TV: The Three Doctors, The Five Doctors et al.) once again to communicate with one another. (AUDIO: The Missing Link)
 * The Master alludes to his part in the Fourth Doctor's regeneration asking if he had ever apologised for the Doctor falling from the Pharos Project radio telescope. (TV: Logopolis)
 * The Master refers to Gallifrey "hiding in its little bubble universe". (TV: The Day of the Doctor, The Time of the Doctor)
 * The Master remembers visiting Gallifrey after the Last Great Time War. (TV: The Doctor Falls)
 * Hakim confidently asserts that he was right all along about a conspiracy theory. (TV: Arachnids in the UK)
 * The Doctor wipes Noor and Ada's memories of everything they witnessed since meeting her. (TV: Journey's End)
 * The Master has left a hologram message for the Doctor, which plays in the TARDIS after he is gone. The Ninth Doctor once did something similar, recording such a message for Rose Tyler as part of Emergency Program One. (TV: The Parting of the Ways)
 * In the hologram, the Master references the Founding Fathers of Gallifrey. (PROSE: The Ancestor Cell, The Infinity Doctors)
 * The Doctor recalls hearing about the Timeless Child from the Remnants. (TV: The Ghost Monument)
 * The Doctor tells her companions that she comes from the planet Gallifrey in the constellation of Kasterborous. (TV: Pyramids of Mars, Attack of the Cybermen, Voyage of the Damned, The Day of the Doctor)
 * The Doctor states that she stole her TARDIS and ran away from Gallifrey. (TV: The War Games, Logopolis, The Five Doctors, Remembrance of the Daleks, The Sound of Drums, The Doctor's Wife, The Name of the Doctor, Heaven Sent; AUDIO: The Beginning)
 * The Doctor has a conversation with Graham through a video recording. The Tenth Doctor did much the same with Sally Sparrow. (TV: Blink)
 * Previously, the Doctor spoke of, who she described as a friend and enemy, to Team TARDIS while tracking a Time Lady who turned out to be the Corsair. However, she does not disclose that Missy and the Master are one and the same. (COMIC: Old Friends)

Home video releases
to be added