For two thousand years, the starship Astron has searched the galaxy for alien life - without success. Now, just as the ship is falling apart, the only direction left to explore is across the Dark, a one-hundred-generation journey through empty space. The ship's captain - immortal, obsessed - refuses to abandon the quest. He will cross the Dark, or destroy the ship trying. Only Sparrow, a young crewman uncertain of his own past, can stand against the captain, and against the lure and challenge of the dark beyond the stars...