If you haven't read The Shadow of Albion, an authors' foreword provides background: "The point of divergence here is the affair of the Duke of Monmouth." Historically, James, Duke of Monmouth and the eldest known illegitimate child of Charles II, led an unsuccessful uprising against his uncle, the Catholic James II, in 1685. He was beheaded and his followers and supporters executed. In Norton and Edgehill's universe, Charles II married Monmouth's mother secretly before becoming king and making a childless state marriage. Upon Charles's death, Monmouth was crowned Charles III, continuing a Protestant Stuart line on England's throne.
It is now 1807. The demon-worshipping Duc d'Charenton, who's known as Marquis de Sade in our world, is conjuring black magic. Though he serves Emperor Napoleon through French spymaster Talleyrand, de Sade plots to find the Holy Grail, exult Satan, and destroy the only remaining member of France's royal family, the dauphin Louis Capet. Louis escaped France aided by the Duke of Wessex, Rupert St. Ives Dyer, an agent for England's intelligence service. He got to Baltimore, New Albion (England's North American Colonies, since no American Revolution occurred) with his wife, Meriel, and then disappeared.
Meriel writes to Sarah, Duchess of Wessex, to beg for help. Sarah, originally from Baltimore in our universe, decides to go to Meriel's aid and see New Albion. Wessex, returning from an urgent mission, follows his wife. Unfortunately, de Sade has been named governor of French Louisianne (no Louisiana Purchase occurred here) and is on his way. All will meet in Nouvelle Orl eèans.
Readers who admired J. Gregory Keyes's Newton's Cannon, Lois McMaster Bujold's A Civil Campaign, and Sharon Lee and Steve Miller's Partners in Necessity will find this series very much their cup of tea. --Nona Vero