Kit Livingstone has been bequeathed by his great grandfather, Cosimo, an apparently impossible task: to piece together a 17th-century map whose fragments are scattered not just throughout this universe but other universes too. Aided by his girlfriend, Mina, herself in Hapsburg-Empire Prague, Kit begins to make progress but realises that opponents, in the shape of the Burley Men, are equally determined to capture the map, and they have a crucial advantage: the ability to manipulate the will of historical figures for their own ends.