Series: 4
Original Air date: April 26, 2008
Number Doctor: 10th
Companion(s): Donna
Writer(s): Helen Raynor
Director(s): Douglas Mackinnon
Guest Stars
Christopher Ryan as General Staal
Rupert Holliday-Evans as Colonel Mace
Dan Starkey as Commander Skorr
Ryan Sampson as Luke Rattigan
Bernard Cribbins as Wilfred Mott
Jacqueline King as Sylvia Noble
Eleanor Matsuura as Jo Nakashima
Christian Cooke as Ross Jenkins
Synopsis: The Doctor gets a call from onetime traveling companion Martha Jones with a request that he return to Earth immediately. She and the military have taken over the ATMOS plant and she needs his help after 52 people around the world all died simultaneously. All had the ATMOS anti-pollution device fitted on their cars so the military has raided the factory believing it to be controlled by aliens. The Doctor learns that the Sontarans are planning to take over the Earth. They take Martha prisoner and she is cloned. Donna meanwhile misses her family and decides to pay them a visit.