In Parks’s domestic thriller, Say Nothing (Dutton, Mar.), a federal judge and his wife are devastated when someone kidnaps their six-year-old twins.

That summer was so hectic. Digging up bodies from long-ago unsolved homicides. Putting people in comas. Double-crossing hedge fund managers. Every day it was just, you know, something. But none of it was what I needed: a plot for a novel I actually felt compelled to read, much less write.

Then one morning, after my most recent idea had collapsed under its own weight, I was jogging when I remembered some advice from a writer friend: “You have to write the book that scares you,” he said. After all, if it scares you, chances are good it’ll scare someone else.

But what, I asked myself as I ran, scares me?

Flash back to an incident a few years earlier, when my two-year-old son got his finger caught in a door and ripped off a chunk of fingernail. I had never been squeamish about injuries, but seeing my son’s blood, hearing his howls, I nearly passed out. That’s when I learned: my children’s trauma would always be far more distressing than my own.

So there I was jogging, thinking about what scared me, and what immediately came to mind was something happening to my children. Like, say, a kidnapping. But why would someone take my (or anyone’s) kids? Money, sure. But from a storytelling standpoint, money is boring. What character might have something else a kidnapper wanted?

I was a mile into my usual route, nearing a bend in the road. I lifted my left leg to take my next stride. By the time I put it down, the answer came to me. A judge. A federal judge. One who is about to hear a case of great consequence. Someone steals his children to blackmail him into rendering a certain verdict.

I started writing that afternoon. To keep things simple, I made the judge’s life a lot like mine. In addition to having two school-aged children, he lives in rural Virginia, he adores his wife, he has this awesome job. And then, piece by piece, I took that idyllic existence and blew it up. The kids. The job. The marriage. Before long, in the book now known as Say Nothing, it’s all in jeopardy.

Having a plot that came out of a place of sheer personal terror opened up an emotional intensity like nothing I had ever experienced as a writer. There were days when I came away from the keyboard totally drained, feeling the hell I was putting these characters through like it was my own. Because, of course, in so many ways, it was.