The Doctor and his companions meet a group of Eternals who are taking part in a space race where enlightenment. But who is sabotaging the race and why is someone going to great lengths to win the prize? And will Turlough carry out his task to kill The Doctor, or is the influence of the Black Guardian to much for him to handle? is the prize Cast Peter Davison (The Doctor), Janet Fielding (Tegan), Mark Strickson (Turlough), Keith Barron (Striker) Lynda Baron (Wrack), Valentine

In 2084AD The Doctor, Tegan and Turlough land on Sea Base 4 just as it comes under attack from the Silurians and Sea Devils; the original owner and masters of the planet Earth. With the threat of a nucleaer conflict that could wipe out the planet; will The Doctor be able to make peace between humanity and the prehistoric reptile; or will he have to revert to another way to save the Earth. Cast Peter Davison (The Doctor), Tom Adams (Vorshak), Nigel Humphreys (Bulic), Ian McCul