The TARDIS brings the Doctor and Mary Shelley to the continent of Zelonia, on the frontier world Draxine — where, many moons ago, the twin citystates of Garrak and Stronghaven bore testament to mankind’s colonial spirit. That was before the sinister death cult of Garrak’s President Harmon took hold — and Garrak annihilated itself, utterly, in an apocalyptic explosion. Before the bones of Garrak’s dead came back to life, and its skeletal citizens began marching, marching, marching on Stronghaven itself.