Hundreds of years after civilisation has been destroyed by nuclear war, the Earth is divided between the Trackers of the Amtrak Federation - a community living in vast subterranean cities - and the Mutes, who have evolved to withstand the radiation that has driven their foes underground. A long war for possession of the overground has killed and enslaved many of the Mutes, leaving only the Plainfolk to resist the Federation. And now the Iron Masters - a powerful people living in the traditions of the Samurai - have joined the battle for dominance. It is time for Steve Brickman, who has long struggled with split loyalties, to finally pick a side. His duty to his own people, the Amtrak Federation, wars against his spiritual bond to the Mute clan M'Call. Honoured with promotion into to the First Family, it looks as though Brickman may choose his home over that of his love's, the pregnant Clearwater. But when Clearwater gives birth to his child at the exact moment that Mount Saint Helens explodes, it looks as if the Mute Prophesy has come to fruition. Meanwhile Roz - Brickman's powerfully psychic kin-sister - and Cadillac, last free living member of the clan M'Call, must travel into the treacherous lands of the Iron Masters to stave off a deadly retribution, whilst becoming embroiled in another land's civil war. Now that the First Family believe Clearwater's child to be the Talisman - heralded messiah of the Plainfolk - their grip tightens as they plan to use this child of prophesy for their own ends. Earth-Thunder, book six of The Amtrak Wars Saga, first published in 1990, concludes Patrick Tilley's internationally best selling science fiction epic.