HD In 17th century London, the Doctor, Adric, Nyssa, and Tegan discover a "comet" that carried alien Terileptils. They must stop the Terileptil plan to infect all of Earth's humans with a plague, but in doing so they inadvertantly set off a different disaster, in "The Visitation." Doctor: Peter Davison. Adric: Matthew Waterhouse. Nyssa: Sarah Sutton. Tegan: Janet Fielding..
