In the fourth episode of the six-part story "The Power of the Daleks," the Doctor (Patrick Troughton) learns the identity of the rebel leader who has enlisted the Daleks in his scheme to overthrow the Earth colonists. Armed with this information, the Doctor hopes to put an end to the Dalek scourge once and for all -- but this, of course, proves impossible. Series regular Annika Wills (Polly) does not appear in this episode. Written by David Whitaker and (uncredited) Dennis Spooner, "The Power of the Daleks, Episode 4" first aired on November 26, 1966; at present, this episode is believed to be lost. ~ Hal Erickson, Rovi