London, the summer of 1795: a season of revolutionary fervour, scientific discovery and vicious murders.
The British government is in disarray, unable to stem the flood of secrets to Paris; betrayals that doom her war efforts to failure. In rural Kensington a group of French emigres are pursuing a scientific dream, the discovery of a planet they call Selene.
The group has fallen under the spell of a beautiful and amoral woman - Auguste de Montpellier who is at once their muse and dark angel. Meanwhile a killer lurks in the back streets of the capital: the victims are all prostitutes and have been paid in French Louis d'Or, the currency of France's spies.
Jonathan Absey is a Home Office clerk whose official task is to smash the French spy ring. Privately however, he has become obsessed with the murders. These interests intersect when he finds himself drawn into the Montpellier circle, yet his pursuit for truth remains obscured through coded letters, opium and conspiracy.
Absey must uncover the mystery before the summer dies; an invasion fleet is being prepared to set sail across the channel and the lives of those on board now rest on his discoveries.
