Ellen May Ngwethu is a young woman with centuries of experience, no morality and the true knowledge. The world she knows is about to end. The Cassini Division, elite defence force of the Solar Union, sends her on a search for the man whose knowledge could save it. A search that takes her from space to the ruins of London, and back; from the margins of her socialist-anarchist world to its most dangerous edge. The Division's orbital forts around Jupiter are the front line in a centuries-long conflict with post-human AIs, whose intentions are unknown but whose powers once extended to shattering Ganymede and building a wormhole bridge to the far future. Their radio-borne viruses blanket the Solar System, keeping most of its resources from humanity's grasp. But are the post-humans less hostile than they seem?