In the conclusion of the two-part story "The Sontaran Experiment," the efforts by the Doctor (Tom Baker) to help revive and repopulate the long-dead planet Earth are stymied by the fiendish experiments of Sontaran warrior Styre (Kevin Lindsay), who hopes to use the surviving humans in his scheme to conquer the entire galaxy. This time around, everyone's fate hinges on the courage of the Doctor's travelling companion Harry Sullivan (Ian Marter). Production of this episode was halted midway when series star Tom Baker) broke his collarbone, necessitating the extensive use of Baker's double Terry Walsh in the finished program. Written by Bob Baker and Dave Marten, "The Sontaran Experiment, Episode 2" was originally telecast on March 1, 1975. ~ Hal Erickson, Rovi