Nebula Award: Best Novella nominee (1966).
On a habitable moon near Tau Ceti, a young man named Comet Jo encounters a devil-kitten and sees a spaceship crash land. One of the people in the spaceship tells Jo that he has to take an urgent message to Empire Star, and dies. Another collapses to form Jewel, a compact, multicolored, multiplexed crystalline entity. Empire Star is the story of Comet Jo's journey to deliver the message, as narrated by Jewel.