In the conclusion of the six-part story "The Ice Warriors," the Doctor (Patrick Troughton) is still figuratively frozen in the earth's "New Ice Age" of the 31st century. Faced with an invasion of Martian Ice Warriors led by the villainous Varga (Bernard Bresslaw), the Doctor persuades scientist Clent (Peter Barkworth) to utilize a powerful ionizer against the enemy. But this counteroffensive tactic yields very strange results. Written by Brian Hayles, "The Ice Warriors, Episode 6" originally aired on December 16, 1967; this episode apparently no longer exists. ~ Hal Erickson, Rovi