Widowed physician Anna Zarides disguises herself as the eunuch Anastasius so that she can move freely in the upper echelons of Byzantine society and investigate the murder of royal connection Bessarion Comnenos, hoping to prove her twin brother Justinian innocent of the crime for which he has been exiled. Nobody she meets in Constantinople makes this easy for her, and many of them have their own reasons for making sure the truth never comes out.
Anne Perry takes a break from her usual 19th- and 20th-century English settings, traveling very far afield to 13th century Constantinople. If her intent was to show why the term "Byzantine" now has pejorative connotations of "devious, surreptitious, and intricately involved" she has succeeded brilliantly. "Anastasius" finds herself floundering in very deep waters indeed, trying to navigate not only currents of imperial and international politics, but also personal vendettas and the ever-present questions of religion.
Unfortunately, it seems like a whole lot of nothing happens in this book. Inside the storyline Anastasius struggles for years to learn anything useful from the major players remaining in Constantinople, while the reader slogs through chapter after chapter without learning anything more.
It does Perry a disservice to market this book as a historical mystery. It works a lot better as a historical novel about revenge.