The book continues the adventures of Oliver Cromwells top agent, Luke Tremayne. As Cromwells government faces conspiracies and uprisings from royalists, republicans, Catholics, religious extremists, and senior army officers, Luke is sent into Wales to assess the level of antigovernment activity and to solve the murder of a local magistrate. Several more murders follow, and in solving them, Luke confronts devious Welsh gentry, seductive women, a band of highwaymen, smugglers, an evil witch, and a major insurrection against the government.