What could be more commonplace than grass, or a world covered over all its surface with numberless wind-whipped oceans of grass? But the planet Grass conceals horrifying secrets within its endless pastures.

An incurable plague has spread to all inhabited planets but one. No one knows why the prairie-world of Grass is exempt. The imperial power of Earth, a Morman-like religion called Sanctity, despatches the Yrarier family to snoop around They are horsey types; the rulers of Grass are understood to hunt. And so they do, but not for foxes, and not on horseback. The true nature of things - the hunters, the hunted and the fields over which they fly - resists unravelling. But slowly, horribly, deliciously, the truth falls out . . .