In the conclusion of the "transitional" six-part Doctor Who story "Planet of the Spiders," the Doctor returns the precious blue crystal to the Great One, the spider-empress of the planet Metebelis 3. As expected, the crystal endows the empress with incredible powers -- too incredible, in fact. The events of the past five episodes cause the Doctor to come face to face with his own fears, shortcomings, and inner demons -- leading, inevitably, to the fourth of his periodic "regenerations" (and a farewell to Jon Pertwee). Written by Robert Sloman, "Planet of the Spiders, Episode 6" originally aired on June 8, 1974, as the final episode of Doctor Who's 11th season. ~ Hal Erickson, Rovi