Earth faces a confrontation with its colonies, the "Outer Worlds." A historian looks back and sees the problem beginning a century-and-a-half earlier, when Aurora got permission to "introduce positronic robots into their community life." No date is given, but fifty years before the story starts, the Outer Worlds established an immigration quota against incoming Terran citizens. The balance of power then tipped. Now war appears likely, and there are rumors that Earth has developed an unknown weapon...
