The Doctor (Peter Davision) and his companions Nyssa (Sarah Sutton) and Tegan (Janet Fielding) arrive on Earth in the 26th century. Almost immediately, they are suspected of causing the disappearance of a group of paleontologists. Little does the Doctor suspect that he is to be forced into another deadly confrontation with an old and much-feared enemy. Written by Eric Saward, "Earthshock" lasted four episodes, the first of which was originally broadcast March 8, 1982. ~ Hal Erickson, All Movie Guide