Near-future Earth suddenly finds itself in a different version of the solar system, one where human civilizations trade and war between planets. Lurking behind those humans: the long-vanished non-human "Builders," who colonized the solar system long ago, seeding it with Earth life. Ward Parke, astronomy enthusiast and presidential advisor, wants to explore this new solar system, but the planets here are on the verge of a genocidal, civilization-ending...