In the conclusion of the four-part story "The Face of Evil," the Doctor (Tom Baker) continues his efforts to make up for his own past misdeeds by disabling the despotic, dangerously schizophrenic super-computer Xoanan. But will he also be able to end the long-raging war between the Sevateems and the Technicians? With this episode, Louise Jameson becomes a series regular in the role of the Doctor's new traveling companion, Leela. Originally broadcast January 15, 1977, "The Face of Evil, Episode 4" was written by Chris Boucher. ~ Hal Erickson, Rovi