The Doctor and her friends are rescued from an icy death in space by two pilots named Angstrom and Epzo, the final two competitors in a race across the galaxy. The final stage of their challenge takes them to a mysterious planet known only as Desolation, where even the water is lethal. Their destination is the Ghost Monument... which the Doctor soon realises must be her missing TARDIS. Reluctantly, the six join forces to cross Desolation and reach the Ghost Monument -- a journey which will force them to uncover the terrible fate of the people who once settled the planet.