Mary Louise Kelly puts her reporting skills to work in novel

david wilson for the boston globe/Globe Freelance

It all started at a kids’ baseball game. One Saturday afternoon, while Mary Louise Kelly was watching her son play, another mother sat down beside her and told an incredible story: While seeking treatment for persistent wrist pain, the woman had undergone an MRI that revealed what appeared to be a bullet lodged in her neck. The woman had no scar and no earthly idea how it got there.

“So I’m staring at this woman at the sidelines of the Little League game,” Kelly said, asking her things like, “Have you had amnesia? Are you a secret agent?” Driving home from the ballfield, the reporter-turned-novelist couldn’t shake the story. The result, published this month, is Kelly’s second novel, “The Bullet,” in which a “very introverted, quiet homebody” tries to track down the story behind her own buried bullet, in essence forced to become an investigator into her own personal mystery.

A former national security reporter for NPR, Kelly said that her experience in journalism is inextricable from her work as a novelist. “Hopefully one complements the other,” she said. “Writing novels — on the one hand you’re making it all up, but to me half the fun is going and reporting and talking to people.”

Already at work on a third novel, Kelly is still following her nose as a reporter. One project involves the woman whose story grew into the book. “I had deliberately not sought out this woman, because I guess I didn’t want to hear what the real-life story was,” she said. “But finally when the book went to press this spring, my curiosity got the better of me,” and the two have been in touch, on the trail of what Kelly called “a real, true, great mystery.”

Kelly will read at 7 p.m. Tuesday at Harvard Book Store in Cambridge.