The Poison Sky (TV story)

"The planets going nuclear!"

Synopsis
The Sontarans activate their masterplan, and begin to choke the whole of planet Earth. UNIT is left defenceless, with a traitor in their ranks. And as interplanetary war edges closer, Doctor has to fight to keep both Martha and Donna alive - but will he have to make the ultimate sacrifice?

Plot
To be added

Cast

 * The Doctor - David Tennant
 * Donna Noble - Catherine Tate
 * Martha Jones - Freema Agyeman
 * Wilfred Mott - Bernard Cribbins
 * Sylvia Noble - Jacqueline King
 * General Staal - Christopher Ryan
 * Commander Skorr - Dan Starkey
 * Colonel Mace - Rupert Holliday Evans
 * Luke Rattigan - Ryan Sampson
 * Ross Jenkins - Christian Cooke
 * Private Harris - Clive Standen
 * Private Gray - Wesley Theobald
 * Newsreader - Kirsty Wark

Production crew
To be added

Story notes

 * Helen Raynor wrote this episode. Her Series 3 episodes Daleks in Manhattan and Evolution of the Daleks both occupied fourth and fith episode in the series. This two part episode also occupies episode four and five.
 * This is part two of a two part story that began with The Sontaran Strategem.
 * This two parter is Douglas Mackinnon's first story as director.

Ratings
To be added

Myths
to be added

Rumours

 * The Sontarans need the gas from the cars to make the earth habitable for themselves.
 * A Rutan army will appear in flashback.
 * Details of the Brigadier's whereabouts are revealed. This seems very likely as in the edited Fear Forecast one of the children reacts to a character that was with a previous Doctor. Given UNIT'S presence, this could well be Lethbridge Stewart
 * The Sontarans steal the TARDIS. Also likely, as again in the Fear Forecast it is mentioned something happens to the TARDIS
 * UNIT will launch a nuclear strike. This is highly likely as the trailer for this episode is set around a countdown at [one of UNIT's bases. Also during the trailer Staal states that: "the planet is going nuclear".
 * The Valiant will be put to good use by Colonel Mace.Something of the Master's is apparently going to appear in this episode according to the Fear Forecast. It is likely to be the Valiant as it is a UNIT ship
 * Donna will kill a Sontaran by the Probic Vent.She is mentioned as trying to get at a probic vent by the Fear Forecasters 
 * The Doctor's hand will reappear. this seems likely as the Fearear Forecast also says something familar on the TARDIS floor
 * The TARDIS will take off with the Doctor, Donna and Martha stuck inside at the end of the episode.

Filming locations
To be added

Continuity
The Doctor wears a gas mask and asks "Are you my mummy?" (DW: The Empty Child, 2005, The Doctor Dances, 2005)

Discontinuity, Plot Holes, Errors

 * In the next time trailer, a corridor is seen exploding with Sontarans inside it. This is the same corridor that exploded in the Torchwood episode Sleeper. This is not a plot hole or error. It is common for TV shows to make use of sets more than once to save on the budget

DVD and other releases

 * It will be released on the Series 4 boxset DVD in November 2008.