Grace Donner never thought she would go to Mars: she was raised in Cloister 11, a low-technology paradise walled off from the world outside. Now she has landed on a frontier world, an alien world—a world whose survival is threatened by loss of the very technology Grace disdains.
Traveling the scarcely-terraformed dunes of Mars and its settled canyons and domes, Grace and her companions desperately search for a way to end the crisis. And in the midst of political ferment, luddite warfare, and technological disaster, Grace will face her own frontier: What is human? What is machine?