At the end of the 21st century, many people believe the only real hope for humanity lies in the Worlds: 41 orbiting satellites housing half a million people. Though the creation of cheap fusion has undermined the Worlds as a source of solar energy, they still welcome many tourists and offer plenty of raw materials for export. For example, New New York is almost pure steel. And, from that city comes Marianne O'Hara, a brilliant political-science student who has elected to spend a postgraduate year on Earth--where she unwittingly finds herself caught up in a group of fanatics looking to start another revolution in America, even if it means the destruction of the planet.