Having finally reached the stars, humanity finds that we are fenced in by an unknown technology. At 22 light-years across, the area cordoned off by the mysterious Pylons is hardly small, though humanity loves to push boundaries. Enter the Dust Bus, a prospector ship cruising between stations when an inert, seemingly deactivated Pylon is discovered. What happens next throws all of human space into a panic and sends ripples across a galactic civilization spanning millions of years and near as many worlds.