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