Some fifty years after the "Doctor" (now Jon Pertwee) helped the King of "Peladon" lift a terrible curse, he and "Sarah Jane" (Elisabeth Sladen) return to it's citadel to find the new queen (Nina Thomas) being controlled by her chancellor "Ortron" (Frank Gatliff) and facing a rebellion from her oppressed mineworkers who are fed up being used as glorified slaves. Added to her misery is the fact that the planet is caught up in some intergalactic furore over that which they are mining - a rare mineral called "Trisilicate" that only exists on "Peladon". Thanks to the help of the miners' leader "Geb...