In the conclusion of the four-part story "The Underwater Menace," the mad Professor Zaroff (Joseph Furst) launches his scheme to empty the oceans and split the world right down the middle. With the help of a fishlike tribe, the Doctor (Patrick Troughton) and his companions stage a counteroffensive, but time is quickly running out for mankind. Written by Geoffrey Orme, Doctor Who: The Underwater Menace, Episode 4 was first telecast on February 4, 1967. ~ Hal Erickson, Rovi