The Poison Sky (TV story)

"We will ravage this planet!"

- Staal

Synopsis
The Valiant clears the ATMOS gas as the Sontarans activate their masterplan to turn Earth into their cloning planet. 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
 * Rose Tyler - Billie Piper
 * 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
 * Captain Price - Bridget Hodgson
 * Private Harris - Clive Standen
 * Private Gray - Wesley Theobald
 * Newsreader - Kirsty Wark
 * Mal Loup - Lachele Carl

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

Filming locations
To be added

Continuity

 * The Valiant last appeared in Last of the Time Lords.
 * At the end of the episode, when the TARDIS flys off, the Doctor says his "What, what, what" line from Donna's first appearence in The Runaway Bride.
 * Rose Tyler appears on the TARDIS scanner screen for a split second. She was last in Partners in Crime. She appears to be shouting 'Doctor!'
 * The Valiant's laser is similar to that of Torchwood 1's used against the Sycorax. (DW: The Christmas Invasion)
 * The Doctor is threatened by Luke Rattigan with a gun. The doctor was previously threatened by Mr Halpen in Planet of the Ood

Discontinuity, Plot Holes, Errors

 * A corridor explodes with Sontarans inside it. This is the same corridor that exploded in the Torchwood episode Sleeper. The corridor in Sleeper was in Cardiff but the one in this episode is in London. A similar mistake occured in Partners in Crime. (Perhaps these buildings are built to the same design.)

Commander Skorr is killed by Colonel Mace with a pistol, but minutes later he can be seen open skinned next to General Stall in the Sontaran ship.

DVD and other releases

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