The Poison Sky

196b – "The Poison Sky"
Doctor Who episode
File:The Poison Sky.jpg The poisonous Sontaran gases (creating the titular "poison sky") above Sylvia and Wilfred's street ignite as the flames from the Doctor's atmospheric converter spread globally.
Cast
Doctor David Tennant (Tenth Doctor)
Companion Catherine Tate (Donna Noble)
Guest Billie Piper - Rose Tyler Christopher Ryan – General Staal Rupert Holliday Evans – Colonel Mace Bridget Hodgson - Captain Price Dan Starkey – Commander Skorr Bernard Cribbins – Wilfred Mott Jacqueline King – Sylvia Noble Ryan Sampson – Luke Rattigan Christian Cooke - Ross Jenkins Clive Standen - Private Harris Wesley Theobald - Private Gray Meryl Fernandes - Female Student Leeshon Alexander - Male Student Kirsty Wark - Herself Lachele Carl - US Newsreader
Production
Directed by	Douglas Mackinnon
Written by	Helen Raynor
Produced by	Susie Liggat
Executive producer(s)	Russell T. Davies Julie Gardner Phil Collinson
Production code	4.5
Series	Series 4
Running time	45 mins
First broadcast	3 May 2008
Chronology
← Preceded by "The Sontaran Stratagem" Followed by → "The Doctor's Daughter"

"The Poison Sky" is the fifth episode of the fourth series of British science fiction television series Doctor Who. It was broadcast on BBC One on 3 May 2008. The episode features both old companion Martha Jones and the alien Sontarans. It is the second of a two part story, following "The Sontaran Stratagem".

Plot

Synopsis

Following from the previous episode, Sylvia Noble manages to free Wilfred Mott from the car by smashing the window with an axe. The Doctor sends Donna Noble back to the TARDIS while he sets off to figure out what the Sontarans are up to. After studying the gas, UNIT determines that it will need to reach 80% density to become lethal. Elsewhere, Martha helps the Sontarans to seize the TARDIS. Realising that he is trapped, the Doctor attempts to goad the Sontarans into revealing their plan: the Sontarans are smart enough not to fall prey to this ploy, but the Doctor does trick them into maneuvering the TARDIS out of the main war room, placing Donna in a position to help.

Against the Doctor's advice, UNIT decides to use nuclear weapons against the Sontarans; however, Martha's clone has covertly copied the launch codes, and stops every attempt they make to fire the weapons. This in itself shows a hidden agenda: nukes would not have harmed them in the first place, which combined with the unidentifiable elements in the gas, suggest that the Sontarans have an interest in keeping anything from disrupting the atmospheric conversion. At the same time, the Sontarans mobilize a contingent of troops to protect the factory. With the Sontarans' ability to jam most conventional firearms by expanding the copper-lined bullets, the UNIT troops are quickly slaughtered and the factory is secured.

Rattigan leaves the Sontaran mothership to gather his students. He plans to take them to another planet and begin the human race anew. The students merely laugh him off, even when he brandishes a gun. When he returns to report his failure, the Sontarans likewise ridicule his efforts, having never planned to take him or his students anywhere. Rattigan teleports back to his mansion before they can kill him, and the Sontarans lock the teleport pods behind him.

Meanwhile, the Doctor instructs Donna on how to reopen the teleport pods. As she makes her way through the ship, UNIT begins a counterattack, loading their weapons with non-copper bullets and using the aircraft carrier Valiant to clear the gas. The counterattack is a success, and the UNIT troops are able to put the Sontarans on the defensive. The distraction allows the Doctor to make his way to the cloning room where Martha is being held. Having figured out long before that the clone wasn't the genuine article, he severs its connection to Martha, leaving it to die. Martha convinces the clone to betray the Sontarans in its last moments, and the clone reveals that the poison gas is actually "food" for Sontaran clones: they are converting the planet into a giant breeding world. With Donna's help, the Doctor is able to reactivate the teleport pods, allowing him to rescue Donna, steal back the TARDIS, and teleport into Rattigan's mansion.

With the equipment Rattigan's students built, the Doctor builds his own atmospheric converter, igniting the atmosphere to clear out the poison gas as shown in the picture. However, he knows the Sontarans won't accept defeat so easily, and teleports to their ship with the converter, planning to give them the choice between retreat or death. Staal chooses the latter, content with the knowledge that the Doctor will die with them, but at the last moment, Rattigan teleports himself to the Sontaran ship and brings the Doctor back to Earth, sacrificing himself to destroy the Sontarans.

With the day saved, Martha prepares to head home. However, before she can leave, the TARDIS suddenly springs to life, locking the doors and piloting itself to places unknown as the jar containing the Doctor's severed hand bubbles.

Continuity

• The Doctor refers to the events of the first series' episode "The Empty Child" when he says "Are you my mummy?" to the colonel whilst wearing a gas mask.
• Brigadier Lethbridge-Stewart is mentioned as being "stranded in Peru", the first explicit mention of the character in the new series. Colonel Mace refers to him as "Sir Alastair", implying he has received a knighthood since the events of Battlefield.
• Just as Donna moves towards the TARDIS screen while the Doctor contacts the Sontarans, Rose Tyler can be seen on the screen, silently calling out. This follows a similar silent cameo appearance in "Partners in Crime".
• The Valiant, the primary setting for the climax of "The Sound of Drums" and much of "Last of the Time Lords", is seen again in this episode when it is used by UNIT to clear the poisonous gas from the atmosphere. It is also equipped with a scaled down version of the Torchwood weapon that destroyed the Sycorax ship in "The Christmas Invasion".
• As the TARDIS traps Donna, Martha, and the Doctor at the end of the episode, the Doctor's severed hand, last seen at the beginning of "Voyage of the Damned", can be seen in a similar state of agitation it felt when the TARDIS materialised near it in the Torchwood episode "End of Days".
• In addition to the Sontarans, the Rutans are mentioned for the first time in the revived series.
• Lachelle Carl reprises her recurring role as the US Newsreader seen previously in the episodes "Aliens of London", "World War Three", "The Christmas Invasion" and "The Sound of Drums" and in Doctor Who spin-off The Sarah Jane Adventures story Revenge of the Slitheen.

Production

This episode and the previous episode were filmed over five weeks, beginning in September 2007. Post-production was completed a week before the first part aired.

When interviewed on Friday Night with Jonathan Ross, Catherine Tate stated that she had been filming alongside ten actors playing Sontarans for two weeks before she realised that there were actors inside the Sontaran costumes. She had assumed the Sontarans "ran on electricity". It was not until an actor removed his helmet to reveal his real face that she realised her mistake. She stated she was "freaked out" by this and said she "nearly died".

When the Doctor interrupts the Sontarans' transmission, animated footage from CBeebies's part live action, part animation eco adventure show Tommy Zoom is brought up on screen featuring the villanous Polluto disguised as a magician and the heroic Tommy and his dog Daniel as his audience.

As in many previous episodes of the revived series, supposed BBC News 24 footage is used featuring reports of unfolding events. However, as with the more recent appearances of such footage in Doctor Who, the channel is simply captioned on screen as 'News 24' devoid of the BBC logo. Since this episode was produced, the BBC News 24 channel was rebranded in real life as BBC News, thus rendering its fictional counterpart as an even more distorted depiction of the channel.

"The Poison Sky" marks the first time all three of the Tenth Doctor's primary companions — Donna Noble (Catherine Tate), Martha Jones (Freema Agyeman), and Rose Tyler (Billie Piper) — have appeared in the same episode, though Rose's appearance was extremely brief.

External links

• The Poison Sky on Tardis Wiki, the Doctor Who Wiki
• "The Poison Sky" at the BBC Doctor Who homepage
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