It is the time of the Reformation. Henry VIII's England moves toward schism; Luther's precepts spread through Europe even as the Inquisition strives to wipe out any hint of heresy.
Franzicco Ragoczy di Santo-Germano-the vampire Saint-Germain-is a successful merchant based in Venice. His lavish lifestyle and rumored cache of magnificent jewels have attracted the wrong sort of attention, and without Santo-Germano's noble-and papal-connections, he might be imprisoned, his property confiscated. Also under surveillance is his mistress, the lovely and talented musician Pier-Ariana Salier.

In the Spanish Netherlands, Ragoczy's publishing business is being investigated by the Inquisition. Coming to the aid of his employees, Ragoczy becomes tarred with the brush of heresy, as does Erneste van Amsteljaxter, a writer whose intelligence Ragoczy finds attractive. Ragoczy does what he can to help her, but must return to Venice when he learns that his fortune there has been embezzled away and that Pier-Ariana has disappeared.

In Venice, things are worse than Santo-Germano expected. Not only has his money disappeared, so has a young man who had been spying on the vampire and his mistress. Santo-Germano is accused of kidnapping and perhaps murder. Another spy has discovered Santo-Germano's true nature and intends to kill him before he can feast on all of Venice!