Doctor Who: The Armageddon Factor (Part 4)

"The Armageddon Factor (Part Four)" is the twenty-fourth episode of of the sixteenth series of the original British science fiction television programme, Doctor Who. It is the 495th episode of the show overall and the fourth chapter in the "The Armageddon Factor" storyline and features Tom Baker as the Fourth Doctor. It was directed by Michael Hayes with a script written by David Fisher. This episode aired on BBC One on Saturday, February 10th, 1979.