Charles Finch’s Victorian sleuth, Charles Lenox, returns for his seventh outing in An Old Betrayal: A Charles Lenox Mystery.

Why did you choose the mid-19th-century as the setting for your series?

Part of it was a simple love of the literature of that period—Trollope, Doyle, Gaskell. I also find it fascinating that it’s the last period we humans will ever truly have to imagine, the last period before television and film. That makes it seem particularly romantic to me, that it’s both close to us, and far off enough that we can’t just pull it up on YouTube.

What are the advantages of making your detective an aristocrat?

I think there’s an element of wish-fulfillment in the way a lot of Americans read British literature—the big country house, the servants, the costume drama feel—and I’m not immune to that. So that was part of the appeal of writing about the aristocratic milieu. On a more practical level, I liked the tension of a well-born detective who perhaps met with the censure of his class for this strange vocation, which didn’t really exist yet.

What challenges does a series present?

Writing any series is difficult. It’s a long voyage at close quarters—there are times when you can’t stand the sight of each other. Maybe the hardest part is realizing how differently readers feel about the series than I do. They come to it once a year for an escape, and expect things to be roughly the same, a little bit of progress, whereas it’s tempting at moments, living with the characters every day, to do something momentous, to take a sharp turn. But doing so kind of forgets the relationship the readers have to the books, which is important, not something to sneer at from Parnassus. Writers are too convinced of their own importance. A series is appropriately humbling in that sense.

What does your next novel, The Last Enchantments, have in common with the Lenox novels?

The Last Enchantments is my first nonmystery novel, about a group of students at Oxford, a contemporary update of Brideshead Revisited. It’s very different than the Lenox books in tone, but it shares with them a kind of romanticized vision of England, a lot of it based on literature actually, which is I think in part what drove me to write both, and also what led me to move there for three years. It’s funny, having written all of these books about England, in a way I’ve exorcised it from my system—the book I’m working on at the moment is set in America and has nothing to do with England.