The Earth has been forgotten. A new empire is rising. No civilization can survive on its own. Our universe is governed by physics and faster-than-light travel was not possible - until the discovery of the Flow, an extradimensional field in which we can enter from certain points in spacetime and be transported to other worlds. Humanity has left Earth behind, in space, and over time, forgotten it as it created a new empire, the Interdependency, whose moral foundation is that no world can survive without the others. The Interdependency is a bulwark against interstellar war and a control system for the rulers of the empire. The Flow is eternal, but it is not static. Just as a river changes course, so does the Flow, cutting off worlds from the rest of humanity. Three individuals in the Empire - a scientist, a starship captain, and the Empress of the Interdependency - embark on a race against time to discover if anything can be salvaged from a collapsing interstellar empire.