Enigma Season

For generations, humankind has lived in protective tunnels and domes on an Earth ruined by war and environmental destruction. To reinforce their fear of the deadly world beyond the domes, children are raised to the litany of The rain that burns, the light that blinds, the air that kills, the water that poisons...In the domes, Enforcers keep an oppressive rule of law, a discipline accepted as necessary for a population sheltering from such a hostile world. The Enforcers are abetted in this by the mysterious Enigmats, aliens who came to Earth many years earlier; no one really knows why the Enigmats are here, but it's generally accepted that they have intervened to protect the human survivors from the consequences of their own folly.