With the Doctor down in the execution pit and presumed dead, the cruel Lady Adrasta threatens Romana in order to gain obedience from K-9 and use his blast ray in a hunting party against the globular alien creature lurking about in her mine tunnels, with additional designs on using the TARDIS to maintain her planetary monopoly on metal. Meanwhile the Doctor, alive, discovers Organon the Astrologer living down in the pit, having managed to avoid death by the strange, house-size alien creature that roams around down there, too.