The Doctor and Romana's mission to find the first segment of the Key to Time is threatened when they are trapped in catacombs on an icy alien world, pursued by both the evil warlord Vynda-K's men and the Ribans.
Danger brings strange allies for the Doctor, Romana and K9 when they are caught between deadly weapons and savage beasts on an icy, alien world.
The Doctor and Romana set out to collect the six segments of the "Key to Time." Their first stop: Ribos, a planet where the inhabitants have reached a Middle Ages stage of development.
