In 13½, Barr’s stand-alone thriller, two formerly abused children meet and fall in love 40 years later, only to discover that “[t]he things that terrorize you are those you don’t see coming.”

What was the biggest challenge for you in writing a stand-alone novel after your successful Anna Pigeon series?

Having written Anna Pigeon for so long, I know her, just as I know the locations where her novels take place. Anna Pigeon was the first solid character I developed, and when I’m working on her books, she takes over. The hardest part of writing 13½ was finding the new voices. I was about a third of the way into this book before they took shape, and then I had to go back and rewrite—and rewrite.

How did you decide to include the fortune-teller character in 13½?

I lived in Mississippi for several years, and later in New Orleans, I worked in an art gallery on Jackson Square, which has a Damon Runyonesque quality. I’d been reading tarot myself for years, and I set myself up as a tarot reader on Jackson Square to see what it was like. I was intrigued with the idea of a believer coming to a reading performed by a reader who knows perfectly well she is making up the material the believer accepts.

This novel balances two major narratives. How did you arrive at their intersection?

There are really four major characters involved, because Polly the child and Polly the mature woman are two different people, just as Dylan, “the Butcher Boy,” and his later identity as Marshall, Polly’s husband, are completely different. They’ve changed enormously over four decades. The young brothers Dylan and Richard came first; Polly came later. Making them intersect was hard work. I had an epiphany when I realized that Marshall had been that boy, but he had become a totally different person.

Are Polly’s attitudes toward love and marriage and children at the close of 13½ going to be reflected in Anna Pigeon’s later development?

Anna started sliding in this direction in Borderline [2009], a novel where in the course of an investigation Anna, a middle-aged woman, was stuck with a baby; it changed her. In my next novel, I’m going to explore that change further. I see it as a result of a very basic, very profound human drive: save the little ones!