In 2526, 8 Earth paleontologists and geologist were investigating a fossil find in a newly discovered case when 7 of them disappear. The only one who seems to have got out is Professor Kyle. She accompanies Lt. Scott and his troop of soldiers into the unmapped caves to see if they can find her colleagues. What they find however is the Doctor and his traveling companions Nyssa, Adric and Tegan who have also just arrived in the TARDIS. They're near the location where the scientific expedition was attacked and Scott suspects the Doctor. There are others in the in the subterranean structures however.
