Overview
"The Zygon Invasion" is the seventh episode of the ninth series of the British science fiction television series Doctor Who. It was first broadcast on BBC One on 31 October 2015, and written by Peter Harness and directed by Daniel Nettheim. The episode is the first episode of a two-part story, the second part being "The Zygon Inversion", which aired on 7 November. In the episode, a peace treaty agreed between humans and shapeshifting aliens called Zygons in the 2013 episode "The Day of the Doctor" has started to fail. A radicalised splinter group of Zygons, seeking to no longer hide among humans but be themselves, takes over Zygon High Command, and seeks to invade present-day Earth and neutralise military organisation UNIT. The alien time traveller the Twelfth Doctor (Peter Capaldi) attempts to keep the peace.
The story was conceptualised by showrunner Steven Moffat, who was deeply impressed by the Zygons' debut story, 1975's Terror of the Zygons, and sought to write a sequel story featuring them that would touch on numerous real-world topics. Moffat asked Harness to help him with writing the overall story, and the two worked together to produce both "The Zygon Invasion" and its second part. The story also focuses heavily on Ingrid Oliver's character Petronella Osgood, The episode was watched by 5.76 million viewers and received positive reviews from critics, who noted the episode's focus on contemporary real-world issues, and praised aspects such as Osgood's characterisation and portrayal, as well as the twist reveal of the Doctor's companion, Clara Oswald (Jenna Coleman), being replaced by a Zygon during the episode's events.
However, the episode's slow pacing was criticised by a few critics, who also noted the episode was hard to judge on its own merits without watching its second part. "The Zygon Invasion" alongside "The Zygon Inversion" were novelised by Harness in 2023.
Plot
Ever since the War, Tenth, and Eleventh Doctors ensured the creation of a peace treaty between humans and Zygons, there existed two versions of UNIT scientist Osgood (Ingrid Oliver): one human and one Zygon duplicate. Twenty million Zygons have been resettled on Earth, peacefully living out their lives disguised as humans. The Doctor leaves the Osgoods the Osgood Box to be used as a last resort should things go wrong. After one of the Osgoods was killed, the other left UNIT and disappeared. In the present, Osgood is captured by a splinter group of Zygons in the town of Truth or Consequences, New Mexico just after sending a warning to the Twelfth Doctor (Peter Capaldi) that the treaty is failing. In London, the splinter group, which seeks to be able to live in their undisguised forms, kidnaps and kills Zygon High Command, leaving a Zygon called Bonnie in charge.
In Turmezistan, Osgood is forced to read a video message declaring the splinter group's intent to go to war. At the block of flats where the Doctor's companion Clara Oswald (Jenna Coleman) lives, Clara is knocked unconscious and hidden in a pod underground. Bonnie takes Clara's place. The Doctor travels to Turmezistan via the aeroplane afforded him by being President of Earth to rescue Osgood. The Doctor and UNIT troops converge on the church Osgood is holed up in. The Zygon splinter group, appearing as the soldiers' relatives and friends, kill the soldiers and flee back to the UK through underground tunnels. The Doctor finds Osgood safe under the church, and they bring a Zygon, injured from a bombing run, aboard their flight back to the UK. The Zygon tells the Doctor that their invasion has already taken place.
In New Mexico, UNIT leader Kate Stewart (Jemma Redgrave) finds Truth or Consequences uninhabited aside from the sheriff, Norlander (Gretchen Egolf). Norlander reveals herself as a Zygon, and prepares to kill Kate. In London, Bonnie tricks UNIT scientist Jac (Jaye Griffiths) into going to Clara's block with UNIT troops, where a lift takes them to a series of underground tunnels and they discover a number of Zygon pods. Finding Clara's pod, Jac realises that Clara was switched with a Zygon. Jac and the troops are killed by the splinter group when they attempt to escape. Bonnie travels to UNIT to obtain a shoulder-fired missile. As Bonnie informs him of the deaths of his friends, she fires a missile at the plane.
Writing and conception
Showrunner Steven Moffat was highly impressed by the Zygons in their debut story, 1975's Terror of the Zygons, and had brainstormed a concept for a sequel to the serial, which would see homeless Zygons settling on Earth and would discuss issues such as immigration, refugees, resettlement, ghettoization, and the radicalisation of factions that led to terrorrism. The Zygons' prior appearance in 2013 special "The Day of the Doctor" was used by Moffat to set up this sequel story, which would be explored in "The Zygon Invasion" and "The Zygon Inversion". Moffat was deeply impressed by writer Peter Harness's work on 2014 episode "Kill the Moon" and was keen to work with him again, believing Harness's style would benefit the "paranoid global conspiracy thriller" Moffat had in mind for the story.
Kate references Harry Sullivan, a companion to the Fourth Doctor who fought the Zygons with him, stating that he created the nerve gas that is mentioned to be used as a last resort if UNIT needs to kill the Zygons. The Doctor's plane, and his status as "President of the World" in times of emergency, was previously used in "Death in Heaven".
Casting
(pictured in 2017) as Osgood, a role she had previously portrayed in several prior episodes Peter Capaldi and Jenna Coleman reprise their main cast roles as the Twelfth Doctor and Clara Oswald, respectively, though Coleman additionally portrays the Zygon Bonnie, who is disguised as Clara throughout the episode. Ingrid Oliver and Jemma Redgrave both reprise their roles as Osgood and Kate Lethbridge-Stewart, respectively, with Jaye Griffiths also returning as Jac after portraying the character in "The Magician's Apprentice" earlier in the series. Cleopatra and Sasha Dickens portray Claudette and Jemima, respectively, who serve as the human forms of Zygon High Command. Gretchen Egolf portrays Norlander. Nicholas Briggs voices the Zygons; though he is uncredited in the episode, he was later credited on its DVD release.
Filming
"The Zygon Invasion", alongside "The Zygon Inversion", were filmed in the fourth production block allocated to the ninth series' filming. Filming began on 5 May 2015 and wrapped on 7 June 2015. Many scenes were shot on location. Several scenes which are set in the UNIT safehouse, such as when Osgood is kidnapped, were filmed at the Old Custom House in Cardiff. Filming involving Clara's apartment building was done in flats in Lydstep, and had previously been used to depict Clara's apartment building in 2013's "The Time of the Doctor". The Barry Shooting Centre on Barry Island was used to depict scenes set in the tunnels the Zygon's had set up a base in. The Canal Park in Butetown, Cardiff was used to depict the playground where the Zygon High Command is kidnapped.
Scenes involving the UNIT base in Turmezistan were shot at MoD Caerwent in Wales, which was also used for scenes in 2015's "Before the Flood" earlier in the series. The FIBUA training ground in Sennybridge was used to depict several scenes set in Turmezistan, including scenes involving the church. The town of Tiscamanita in Fuerteventura in the Canary Islands was used to depict scenes set in Truth or Consequences. Scenes set inside of the cavernous Zygon base were recorded in studio, as were scenes set inside of the presidential plane. Computer-generated imagery work in post-production was focused largely on the Zygons' transformations and their "stings", which could kill people via lightning shot from their hands.
Broadcast and reception
The episode was watched by 3.87 million viewers overnight in the UK and received a 19.4%. It received an Appreciation Index score of 82. Overall the episode had 5.76 million viewers. The story had a repeat airing, on 6 November 2015, which garnered 0.18 million viewers.
Critical reception
"The Zygon Invasion" received positive reviews. Based on 19 critic reviews, the episode holds a score of 95% on Rotten Tomatoes, with an average score of 7.74/10. The site's consensus reads "With "The Zygon Invasion," Doctor Who delivers a thrilling episode that pays special attention to character development and the consequences of time travel". Patrick Mulkern, writing for Radio Times, regarded the episode as being "the closest Doctor Who has ever dared come to commenting on the woes of the world," noting its allusions to real-world issues such as training camps, splinter groups, and radicalisation. Ross Ruediger of Vulture regarded the episode as a rare foray into real-world commentary, which Ruediger felt hadn't been done much in recent years of the programme. Alasdair Wilkins, writing for The A.V.
Club, noted that the focus on contemporary issues notably set this episode apart from prior stories, which tended more to focus on the philosophical aspects of a moral dilemma rather than how it connected back to the real world. Wilkins noted that while the story did not directly make comparisons to specific groups or events, its allusions to them allowed the story to ground itself in real-world topics and give viewers an opportunity to reflect on how it relates to the real world. Mulkern highlighted the performances of the cast, namely Ingrid Oliver as Osgood. Kaite Welsh of IndieWire particularly praised the usage and character of Kate, who she felt was a deeply engaging and morally gray character, while also highlighting the expansion of Osgood's character from her prior appearances.
Several critics also praised the twist of Clara being a Zygon throughout the episode, finding it to be well done reveal, though Wilkins felt it served only to highlight the weak overall characterisation of Clara, feeling that the twist worked solely because a viewer, at first glance, would not notice out of character moments for Clara. Wilkins also noted this slow pace served to set up "The Zygon Inversion", though he felt it meant that the strengths of "The Zygon Invasion" would only be determined after "Inversion" aired. Pastes Mark Rozeman similarly felt that many of the episode's subplots, such as Kate's exploration in Truth or Consequences, were weak and dragged down the episode's pace, and also felt that it was hard to judge the episode without knowing how its second part would end.
Commercial releases
A novelisation of this episode and "The Zygon Inversion" written by Peter Harness was released in paperback on the 13th of July 2023 under the title The Zygon Invasion as part of the Target Collection. "The Zygon Invasion", alongside "The Zygon Inversion", were included on a DVD and Blu-Ray release of the second half of series 9, which was released on 4 January 2016. A complete release featuring the entire series was released two months later on 7 March 2016, which included a number of extras and deleted scenes from the episodes. Music from the episodes were included on series 9's soundtrack release in April 2018.