UNDER THE CONTROL OF THE TIME LORDS, the TARDIS takes the Doctor and Jo Grant to the planet Uxarieus. There they meet a group of human colonists living with the indigenous ‘primitives’ in a state of uneasy truce. A mining robot is secretly prospecting nearby. When two colonists are killed, seemingly by a giant lizard, the Doctor investigates but is attacked by the robot. The machine’s assault is checked by the arrival of Caldwell, a mineralogist with the Interplanetary Mining Corporation.