In the third episode of the four-part story "The Keeper of Traken," the Doctor (
Tom Baker) and Adric (Matthew Waterhouse) continue their efforts to find a worthy successor for the present Keeper (Denis Carey), lest the precious Union of Traken be dissolved. Among the candidates is a dignitary known as the Melkur (Anthony Ainley) -- who turns out to be an old and dangerous enemy of the Doctor's. Written by Johnny Byrne, "The Keeper of Traken, Episode 3" originally aired on February 14, 1981. ~ Hal Erickson, All Movie Guide