PW: You're publishing your 10th ancient Roman mystery about Gordianus the Finder, The Judgment of Caesar. How did the series begin?

My first trip to Rome was a life-changing event. I'd been studying ancient Rome since childhood, and to actually touch the ruins in the Forum was electrifying. I was starting to read mystery fiction at about that time and found myself craving a mystery set in ancient Rome. The closest thing I found was more like true crime—Cicero's speech defending a man accused of murdering his father. To hear Cicero tell it, the more he discovered about the real crime, the greater his own personal danger, and I found myself thinking this would make a terrific novel. To anchor the book, I gave Cicero a sleuth, Gordianus the Finder.

Why did you choose to write historical mysteries rather than standard historical novels?

Murder, the greatest possible breach of the social fabric, is the Pandora's box that allows all the other secrets in the story to come tumbling out. Revealing hidden truths is the ultimate aim of both historical and mystery fiction. I also like the built-in Aristotelian structure of the mystery form. By definition, a mystery must have a beginning, middle and end. Everything is geared toward delivering a strong resolution.

Is there a historical basis for the character of Gordianus?

While I don't know of any evidence for private investigators in Republican Rome, that doesn't make the idea far-fetched. It was an era of vicious litigation and scandal-mongering, so it makes sense that powerful people would hire expert outsiders to dig up the dirt on opponents or sniff out threats from enemies. If indeed there were such professionals, we wouldn't expect to find evidence of their existence, because they'd be invisible in the historical record.

What limited your use of historical figures such as Cleopatra in The Judgment of Caesar?

I never contradict the known facts. I work inside the gaps in the historical record, which usually gives me all the leeway I need. I do tend to go for the subversive approach. History is written by the victors, inevitably biased, so I always try to turn "common knowledge" on its head. As for Cleopatra, one of the frustrations we moderns must contend with is that the ancient historians simply couldn't imagine writing the biography of a woman!

How did you go about using such gaps in your plot?

It seemed to me that the story not told by either novelists or historians is about the relationship not between Caesar and Cleopatra—that's been done a thousand times—but between Caesar and Cleopatra's teenaged brother, King Ptolemy, her rival for the throne. As the loser in the contest, Ptolemy is always belittled—movies and books show him as a snotty brat—but there's no reason to assume he was any less charismatic than his sister, and there's a lot to be read between the lines in Caesar's own account of their relationship.

What have your studies taught you about the limits of history?

Living a kind of split existence, partly in the ancient past and partly in the present, I reflect a great deal not just on the limits of history but on the limits on any kind of knowledge. We have a pretty good idea of the forces that caused the civil war between Pompey and Caesar—but I'm not at all sure why we went to war in Iraq. In some ways the past appears more clearly to us, because of perspective; but any illusion of certainty is just that—an illusion. The sand beneath our feet is constantly shifting.

What's next?

I'll switch gears before Gordianus is on the scene for the assassination of Julius Caesar because my next project is an epic fictional biography of the city itself.