When the planet Archetryx is threatened with a Dalek assault squad, the physician and Evelyn become embroiled in an ever-deepening mystery. What has become of Chief executive Romana, lacking for twenty years? What lurks in the vast gravity wells of Archetryx? What’s the secret of the historic component the Daleks are synthesising – and how will Gallifrey feature in the plans? The Doctor discovers that if his oldest enemies cannot conquer the universe they will watch it rise in flames…