With England moving towards war with the Dutch, a court official is found murdered at a private establishment run by Chaloner's friend Temperance. The death appears scandalous rather than political, but connections soon emerge with the radical Fifth Monarchists.
Ordered to penetrate the sect, Chaloner discovers links between the victim, military preparations and the destruction of a naval vessel. Rumour and genuine conspiracy are difficult to separate, and he must determine whether the radicals are planning an uprising or being used to disguise treason within the defence establishment.