Ancient documents are discovered near Safed in the Holy Land. Friar Roger Bacon at Lincoln Castle and Thomas, a peasant boy with artistic talent, preserve the contents of the papyri in the form of an illuminated codex written in a secret code. Thomas is assisted by his former classmate Amelia St. Denis about whom he makes a tragic discovery. The codex is buried in the library of Lincoln Cathedral where three centuries later it is sold to Holy Roman Emperor Rudolph II. With the help of the angel Madimi, Dr. John Dee and scryer Edward Kelly decode the text. Kelly meets an ignominious end.
Rudolph gives the codex to his favorite courtesan. What follows is a chilling account of the bloody deeds of one Countess Erzsbet Bthory while under the influence of the codex during her stay in Prague Castle.
Though frustrated in her quest to find a proper custodian for the book, Madimi continues her search. The Earl of Wickshire is the new recipient giving rise to the tragic tale of how a decent man was brought low through his possession by the codex.
Armed with the book a century later, Sir Alexander Perceval declares himself a prophet and founds a club of libertines whose motto is Fay e que vouldras. He runs afoul of George III.
The angel Madimi continues her search.
The Cambridge Apostles, poet, scion and headmaster, find something to talk about. What the headmaster sought to conceal is revealed by a famous forensic investigator.