Longtime mystery writer Nevada Barr (Anna Pigeon series) launches her first stand-alone thriller this month. Speaking in a phone interview from her home in New Orleans, she shared some background on the exciting, psychologically draining 13½ (LJ 8/09) and offered a sneak peek at her other writing projects.

Can you explain the significanceof the title?

That was a gift to me. I was talking to a psychiatrist friend of mine who works with juveniles. He told me the trend in the prison where he worked was that the inmates would get 13½ tattooed on their bodies. It stood for 12 jurors, one judge, and half a chance. I had to fight for it because the publishing world does not like numbers, and they really don't like fractions!

What got you thinking about this type of crime?

When I lived in Minneapolis years ago, and we're talking years ago, there was a nice boy from a nice family in Rochester, MN, who one day took an axe and butchered his family. The novel is not about him, of course; that was just the inspiration. But it was the first horrific crime that entered my world. When someone is arrested for doing something horrific, you think, "Ask them why. Ask them why they did it." But the answer is always so unsatisfying.

And so I got fascinated with trying to find a "why." I liked the sense of our hero trying to figure himself out. And I've also been fascinated with the concept of who would you be if you found out that everything that you believed about yourself wasn't true.

Was it difficult to juggle all the narrators? Which was the hardest voice to write?

The young Dylan was the easiest, for some unknown reason. But I have been writing—well, I'm working on my 17th Anna Pigeon. That's just, you know, a helluva long relationship. And she's so in my head that to create new voices is hard for me. The most difficult one was Richard's [Dylan's brother]. The Woman in Red [a tarot card reader] came easily, too. I don't know what that says about me! [Laughs]

I've known how to read tarot for years; I picked it up on tour once when I was too bored to do anything else on the airplane. I set up my kit and went down to Jackson Square every day and read tarot and got to talking with the folks who hung out there. It's kind of a whole, sort of dark, Damon Runyon setup.

Your novel is set in a large city (New Orleans), yet this reader felt that the characters were quite isolated. Were you consciously trying to build up that sort of "closed room" tension?

I was, because this book was started during Katrina. It was begun about four months before, and then Katrina hit. I was one of the first people to move back here, and I was the only person in my neighborhood for weeks, with the military going by. And the after-Katrina thing down here was very much a sense of scrambling to get things done with no help.

Was it exciting to be writing a stand-alone? Do you want to do it again?

It was very exciting and very scary. An odd thing occurred. I felt like I was cheating on Anna at first. [Laughs] I didn't want her to know! It was scary because I'd never done a thriller. With mystery you don't want to do formula, but there is a solid through-line in a mystery. Without that backbone—the spine that I'm so used to, building my body around it—was like free fall a lot of the time. Well, it was a rush when it was working and terrifying when it wasn't. Because sometimes you're in free fall, and you know you've got a bungee cord, but sometimes you think, "Did I tie that knot right?"

It sounds like you're going back to Anna. Where's she going this time?

She's going to New Orleans because I've been wanting to do an Anna Pigeon in the Jazz National Historical Park. The rangers are singers. You go in there, and they're singing, playing the guitar and the piano, and they sound dynamite—and they're in green and gray uniforms, with little gold badges. It's just too cool.

But are you cheating on Anna again?

I am so bad. I am working on a young adult book with Julie Smith for ages nine to 14, and it's filled with animals. I just love writing about animals!