On a dark frozen planet where no planet should be, in a doomed city with a sky of stone, the last denizens of Earth's long lost twin will pay any price to survive, even if the laser scalpels cost them their love and hate and humanity. And in the mat-infested streets, round tea time, the Doctor and Nyssa unearth a black market in second hand body parts and run the gauntlet of augmented police and their augmented horses. And just between the tram-stop and the picturehouse, their worst suspicions are confirmed: the Cybermen have only just begun, and the Doctor will be, just as he always has been, their saviour...