In the distant future of Australia, the greenhouse effect is no longer a problem - until an ancient anti-greenhouse engine in space manages to switch itself on. Only the Highliber of Libris can devise a solution, with the aid of her mighty Calculor and her strange ally, the mysterious Abbess Theresla of Glenellen. Or can she? Across the deserts to the north, an escaped component has built a rival calculor, and a renegade librarian is organising an invasion. Which Calculor will win - or is there some quite new factor at work in the politics and battlefields of 40th century Australia?