Doctor Who: State of Decay, Episode 2 (1980)

In the second episode of the four-part story "State of Decay," the Doctor (Tom Baker), Romana (Lalla Ward), and Adric (Matthew Waterhouse), still lost in E-Space, have landed on a feudalistic planet run by three mysterious, highly intelligent Lords. The Doctor eventually discovers that the rulers are from Earth and that it was on this planet that his own race, the Time Lords, first developed their aversion to violence. If this is true, why does it appear that the Lords keep themselves alive by feeding on the other residents of the planet? First shown on November 29, 1980, "State of Decay, Episode 2" was written by Terrance Dicks. ~ Hal Erickson, All Movie Guide