Spearpoint, the last human city, is a vast atmosphere-piercing spire. Clinging to its skin are the zones, a series of semi-autonomous city-states, each of which enjoys a different - and rigidly enforced - level of technology. Horsetown, for example, is pre-industrial, while in Neon Heights they have television and electric trains. Following an infiltration mission that went tragically wrong, Quillon has been living incognito, working as a pathologist in the district morgue. But when a near-dead angel drops onto his dissecting table, Quillons world is wrenched apart one more time, for the angel is a winged posthuman from Spearpoints Celestial Levels - and with the dying body comes bad news. If Quillon is to save his life, he must leave his home and journey into the cold and hostile lands beyond Spearpoints base, starting an exile that will take him further than he could ever imagine. But there is far more at stake than just Quillons own survival...