The Zygon Inversion

"The Zygon Inversion" is the eighth episode of the ninth series of the British science fiction television series Doctor Who. It was first broadcast on BBC One on 7 November 2015, and was written by Peter Harness and Steven Moffat and directed by Daniel Nettheim. The episode is the second of a two-parter, the first being "The Zygon Invasion", which aired on 31 October 2015.

Set in present-day London, the episode involves Bonnie, the leader of a splinter group of shapeshifting aliens called Zygons, taking the form of the Doctor's companion Clara Oswald (played by Jenna Coleman). Bonnie intends to use an object called the Osgood Box to unmask 20 million Zygons on Earth, thereby starting a war against humanity.

The episode was watched by 6.03 million viewers and received positive reviews, who praised the episode’s political themes and Capaldi and Coleman’s performances.

Plot
In the present, Bonnie, the leader of a splinter group of shapeshifting Zygons, has taken Clara's form, keeping her body in a pod. Clara finds herself in a dream version of her flat, able to control Bonnie's actions to a small degree due to a telepathic connection between them, giving the Twelfth Doctor and UNIT scientist Osgood time to parachute out of their plane before Bonnie shoots it down.

The Doctor and Osgood land on a beach. Controlling Bonnie's hand, Clara sends a message to the Doctor's phone saying "I'm awake." The Doctor video calls Bonnie. From winks Bonnie exhibits, the Doctor recognises that Clara is telling him her pod is in London. In interrogating Clara via their telepathic connection, Bonnie learns the Osgood Box is in the UNIT Black Archive under the Tower of London. Against the wishes of the Zygons who are not aligned with the splinter group, Bonnie intends to start a war against humanity by using the Osgood Box to unmask 20 million Zygons on Earth. UNIT leader Kate Stewart, having survived the encounter with the Zygon in New Mexico, reconvenes with the Doctor and Osgood in London.

Bonnie discovers that there are two identical Osgood Boxes in the Archive, only differing by colour. By the time the Doctor, Osgood, and Kate arrive, Bonnie has found that either box's button reveals a second set of two buttons within. When Bonnie prepares to press a button on the blue box, which would either unmask the Zygons or make their human forms permanent, Kate prepares to do the same on the red box, which would destroy either every Zygon or everyone in London. The Doctor tries to talk both of them out of this action – the Osgood Boxes have been a means to assure peace because of the consequences of declaring a war. Eventually, after the Doctor admits the consequences he had to live with since the Time War, both Bonnie and Kate back off with the former realising the boxes are empty and were only a ploy to avoid a disaster. The Doctor wipes Kate's memories to keep the peace treaty. Bonnie calls off the splinter group and says they will live peacefully. Later, the Doctor offers Osgood a chance to ride in the TARDIS, but she refuses and instead reveals her new duplicate – Bonnie, who has taken a new form after giving up Clara.

Continuity
Kate Stewart describes her gunfire while escaping an attacking Zygon as "five rounds rapid". This is a phrase closely associated with Kate's father, the Brigadier, that he first used in The Dæmons (1971).

The Fourth Doctor's companion Harry Sullivan is mentioned in this episode by name (he was only alluded to in the prior episode) as developing Z67 – "Sullivan's Gas" – as a means of stopping the Zygons. The Doctor also refers to Sullivan as "the imbecile", a reference to the Fourth Doctor serial Revenge of the Cybermen, where the Doctor shouted "Harry Sullivan is an imbecile!" after Sullivan triggered a rockslide and then tried to remove a Cyberbomb from the Doctor without deactivating the booby trap.

UNIT's Black Archive, first seen in the Sarah Jane Adventures story "Enemy of the Bane" (2008) and containing items from several past episodes, currently has a Mire battle helmet first seen in "The Girl Who Died" (2015). The Doctor claims that he himself planned to use a box with a button to commit mass murder. This is a reference to "The Day of the Doctor" when three of the Doctor's past incarnations planned to use the Moment, a Time Lord doomsday device, to end the Time War.

Osgood says that there has been more than one meaning for the acronym TARDIS. The 'D' in TARDIS has been given as both "dimension" and "dimensions" during both the classic series and the revival, giving the name TARDIS two different meanings. In "The Next Doctor" (2008), Jackson Lake says his 'TARDIS'—in reality, a hot air balloon—stands for “Tethered Aerial Release Developed In Style”. In this episode, the Doctor gives it yet another meaning: "Totally And Radically Driving In Space".

As he departs, the Doctor tells the Osgoods that "I'm a very big fan", the same thing Osgood says to the Eleventh Doctor in "The Day of the Doctor".

Outside references
The Doctor's Union Jack parachute prototype (calling it "camouflage... we're in Britain.") is a direct reference to the pre-titles sequence of the 1977 James Bond film The Spy Who Loved Me, in which Bond jumps from a cliff and expands a parachute with the same design.

The Doctor calls Bonnie "Zygella", a pun on chef Nigella Lawson's name.

Bonnie is asked by the Doctor about the "brave new world" her revolution will create, citing William Shakespeare's play The Tempest: "O brave new world, that has such people in it".

The Doctor borrows the phrase "And I mean that most sincerely" from the UK television show Opportunity Knocks.

Broadcast and reception
The episode was watched by 4.22 million viewers overnight in the UK, a 20.4% audience share. It received an Appreciation Index score of 84. The final ratings were 6.03 million viewers with a 25.1% audience share.

Critical reception
"The Zygon Inversion" received positive reviews, with many highlighting Capaldi and Coleman's performances and the episode's political themes as its best attributes. On review aggregator Rotten Tomatoes, the episode has a 95% positive review rating and a score of 8/10, with a critical consensus stating, "While "The Zygon Inversion" isn't the most compelling conclusion to a Doctor Who two-parter, it allows for a stirring performance by Capaldi while hinting at Clara's fate in the episodes to come."

Steven Cooper of Slant Magazine called it the best episode of the season so far and claimed it was "a powerful conclusion to the story set up last week". Mark Rozeman of Paste Magazine praised the transformation from "standard aliens-invade plot line" to "a treatise about war and its ultimate uselessness." He ultimately awarded the episode an 8.8. Kaite Welsh of IndieWire heavily acclaimed the episode, awarding it an A++ grade and saying that the episode was "Less overtly political than the previous episode, this week is an embarrassment of riches". She further praised Coleman's performance by saying that the episode "could very well be Jenna Coleman's goodbye present". Mark Rozeman of Paste Magazine awarded the episode a score of 8.8 out of ten, praising Clara and Bonnie's sequences as "brilliantly conceived". He also praised Capaldi's performance, stating "it’s a firm reminder of how lucky we are that an actor of Peter Capaldi’s caliber has taken the titular role and so thoroughly made it his own".

Writing for The Guardian, Dan Martin also heavily praised the episode, specifically the Doctor's anti-war speech in the episode's conclusion. He stated "This Doctor has never been written better, Capaldi has never channelled Tom Baker more, that sequence is cemented instantly as the 'Capaldi moment' in clip shows for the rest of time", and while he said that "It was a risky game to attempt the sort of contemporary allegory" that the episode did, he soon confirmed that the episode "knocked [it] out of the park". Alasdair Wilkins of The A.V. Club also acclaimed the episode, awarding it a perfect "A" grade – the third of the season. He began his review by saying "The climax of 'The Zygon Inversion' makes explicit something that the best anti-war Doctor Who stories have always understood. Depicting the madness of war doesn’t require an epic scale. If anything, narrowing the focus to a single conflict or moral dilemma clarifies the essential futility of violent conflict". He then closed his review by claiming "The simplicity of [the] setup allows this two-parter to be one of the show's strongest ever statements against war, not because the Doctor is challenging us from on high to live up to his standard, but rather because he wants no one else to know his pain". Den of Geek praised ″The Zygon Inversion″ as the best episode of the current series, and named it, ″one of the best pieces of screen entertainment of the year, full stop.″

The episode aired a week after the crash of Metrojet Flight 9268 in Egypt, and resulted in 31 complaints to the Office of Communications (Ofcom) because of the scene depicting a plane being shot down. Viewers argued that the scene was inappropriate in the aftermath of the crash, but Ofcom decided not to launch an investigation. The regulator concluded that "the science fiction nature of Doctor Who and the storyline created a sufficient distinction from recent events".

In print
A novelisation of this episode and "The Zygon Invasion" by Peter Harness was published under the title The Zygon Invasion on 13 July 2023.