Orphaned twins, Meagan and Carl Cadet, share an honored path--they're horse herders. But the horses they herd are unique, for each horse grows beautiful clusters of unicorn-like horns made of living quartz. Like fingerprints, each is dazzlingly different from the other. The horses use these horns to travel through mystic passages, finding new planets for humans to colonize. Meagan and Carl are teenaged equestrians who make perfect caregivers for these unusual horses--if they can avoid the merciless Raiders. Raiders stalk horse herders; capturing them to work their mines, using them until death finally takes the poor humans away from their endless misery. Once taken, no human has been able to escape the brutal grasp of these mysterious aliens.