The Lady Ann Segrim has been murdered, and a Regent Master has been taken at the scene of the crime, red-handed. The suspect is William Falconer, but, strangely, he doesn’t deny the charges. Using Falconer’s own logical methods to solve the crime, Symon, along with Saphira Le Veske, Falconer’s new lover, sets out to clear his name, uncovering an extraordinary plot in the process.