Plot summary
The plot concerns the efforts of an astronaut and geologist/anthropologist, known to the natives as "Purple", to escape from a primitive world on which he is stranded and return to his people. The events are seen from the perspective of Lant, one of the natives, who becomes, in the course of the novel, Speaker (chieftain) of his people.
The natives, a fur covered people, believe in magic and the book shows how sufficiently advanced technology would be perceived by a primitive society.
Purple lands in an egg-shaped vehicle. He casually disrupts the lives of Lant's people, and thoughtlessly demeans Shoogar, the village magician. Shoogar gets revenge by destroying Purple's vehicle, which results in an atomic explosion. Many of the villagers are dead or injured: the rest, including Lant and Shoogar, are forced to flee. Purple is presumed dead.
The villagers eventually wind up on a fertile peninsula, which, as the summer approaches, is rapidly becoming an island (thanks to the influence of the two suns, the shorelines on this world are somewhat variable). To the annoyance of the existing inhabitants of the area, the villagers contrive to be trapped in the verdant area by the rising seas. The villagers are less happy when they learn that Purple is here, serving ineffectively as local magician, having succeeded the incumbent, Dorthi, by killing him by landing on him in a fall from the sky in an impact suit.
Lant's people wish to flee, but have nowhere to go. Lant, who becomes Speaker of the villagers more or less by default, and the local Speaker persuade the two magicians to swear to a peace treaty.
Purple can call his mother ship to get him, but must return to the distant area of the old village to do so. Everyone is stranded on the island for a considerable length of time. Purple conceives the idea of fabricating a flying machine to return him to the area. He persuades his villagers (who are actually anxious to get rid of him) and Lant's, to join in the scheme.
The ship will have balloons, sails, and pedal-driven steering. A good part of the book deals with the tribulations of Purple in trying to create this work, beyond the technology of the local people. He creates 'aircloth' (a thin, airtight cloth), a rubber-equivalent, and splits water into hydrogen and oxygen. He is successful in building the ship.
But in so doing, he has changed the lives of the villagers forever. Not only do they have these new technologies, but he has created problems with crime, intoxication, the ecology, and has altered the relationship between the sexes. In addition, he has introduced money into the culture.
Purple, Shoogar, Lant, and Lant's adult two sons take off for the old village. They get there, and Purple is able to summon the mother ship and depart. There is a brief epilogue—after the return home, Lant notes that a new flying machine, much larger than the first, is to be built, thus continuing the industrial revolution started by Purple.
