In the conclusion of the four-part story "The Krotons," the Doctor (Patrick Troughton) joins forces with scientist Beta (James Cairncross) in a last-ditch effort to destroy the highly advanced but eminently dangerous Krotons. Alas, these efforts may well come to naught, as the Krotons prepare to escape the planet of the Gonds, with the Doctor and Zoe (Wendy Padbury) as their captives -- and principal "energy sources." Written by Robert Holmes, "The Krotons, Episode 4" first aired on January 18, 1969. ~ Hal Erickson, Rovi