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 tramstop 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...