Humanity has spread to every star within 500 light-years of its half-forgotten origin, coloring the sky with a haze of habitats. Societies rise and fall. Incautious experiments burn fast and fade. On the fringes, less modified humans get on with the job of settling a universe that has, so far, been empty of intelligent life.|
The ancient starship But the Sky, My Lady! The Sky! is entering orbit around a promising new system after a four hundred year journey. For its long-lived inhabitants, the centuries have been busy. Now a younger generation is eager to settle the system. The ship is a seed-pod ready to burst.
Then they detect curious electromagnetic emissions from the system's Earth-like world. As the nature of the signals becomes clear, the choices facing the humans become stark.
On Ground, second world from the sun, a young astronomer searches for his system's outermost planet. A moving point of light thrills, then disappoints him. It's only a comet. His physicist colleague Orro takes time off from trying to invent a flying-machine to calculate the comet's trajectory. Something is very odd about that comet's path.
They are not the only ones for whom the world has changed.