Del lives in a world of many skies: by passing through the Hoops embedded in the ground, her people can walk freely between land that lies beneath a new set of constellations for every circuit they make around the edge of a Hoop.

When archaeologists find a copy of the famed Book of All Skies, Del takes delivery of the manuscript in her role as conservator at the Museum of Apasa, hoping it will shed light on the fate of the Tolleans, the ancient civilisation that produced it. But when the book is stolen, the theft sets in motion a series of events that will see her travelling farther than she had ever imagined possible, and her understanding of her world and its history irrevocably transformed.