They thought Earth would always abide. But it hadn't, not at all . . . .

Zoya Kundara has lived on the space vessel Star Road for 250 years. As Ship Mother, she is awakened from Deep Sleep in times of crisis, providing counsel to generations of its Romany crew. Now the starship has returned home, only to discover an Earth on the verge of extinction, blanketed in a crystalline substance called Ice. But it's not ice. This pearl-white mantle is a grand and mysterious ecology of information-bearing crystals. And it is relentlessly enclosing the last free lands.

To find a home for her crew, Zoya must approach the denizens of this strange new Earth. She will discover the Ice Nuns, who seek sole control of the physics-defying crystals; people huddled like moles in underground techno-warrens; and the snow witches, creatures of Ice, both mad and prophetic . . . and one snow witch in particular, who will defend the kingdom of Ice with power and immortal cunning.