Season 19, Episode 118 - "Four to Doomsday"
18 January, 1982
The Fifth Doctor, Nyssa, Tegan and Adric arrive on a spaceship which is headed for Earth. On board they meet natives of Earth from various different eras, and also three Urbankans: Monarch, Persuasion and Enlightenment. What are the aliens' intentions when they reach Earth?
