Season 6

This season featured the first ever UNIT story, The Invasion, which showcased the return of Brigadier Lethbridge-Stewart. It also featured the first official appearance of Time Lords and the as yet unnamed Doctor's home planet (another member of Susan and the Doctor's race, the Monk, had appeared previously, but without much elaboration and without using the term "Time Lord"). It also marked the tenure of Patrick Troughton as the Second Doctor. It consisted of seven serials and forty-four episodes, including two epic-length storylines: the eight episodes of The Invasion and the ten-episode The War Games.