WASHINGTON – Most of the time people see a mouse in the kitchen? They get a trap or call the exterminator. That’s about it.

For Irish crime writer Tana French, a nocturnal encounter with a mouse got her to thinking about a “sense of invasion. It’s your house, you’re supposed to control who goes in and out.”

The 39-year-old is telling this story in her friendly, fast-paced patter (she has only a fleck of an accent). She’ll retell it that night to a standing-room-only crowd at a nearby bookstore, regaling fans with the tale of the beginnings of her pleasingly complicated new thriller, “Broken Harbor.”

It’s a book with a lot more on its mind than pest control. There are real horrors – murder, financial ruin – and imagined, with things in the walls that might or might not be there. It’s getting the rave reviews that have become standard for the former stage actress since she debuted four years ago with her Edgar-winning “In the Woods.”

She thinks about inhabiting her characters as she did her stage roles, searching for that right voice. Although she’s not a fast writer – she starts with a premise and narrator and no outline – she got off to a blazing start on her second career. “Woods” has sold nearly a million copies in the United States and racked up sales worldwide.

The connective tissue of her books is the fictional Dublin Murder Squad, with a different character playing a prominent role in successive books. She gives ace (if cocky) Detective Mick “Scorcher” Kennedy the first-person narrative here, letting him relate his investigation into a killing in a oceanside housing estate. The Spain family – Patrick and Jenny and two kids – seem to have gone mad.

The kids are found dead, and Patrick is stabbed to death. Jenny, also stabbed, is next to her husband, barely alive. There is no murder weapon. Walls are full of neatly made holes. Video monitors are everywhere.

Kennedy, a suicide-haunted man, has dark connections to the place.

This sprawling nightmare stems primarily from that half-seen mouse.

“My husband had been slaughtering zombies on the Xbox, so when he came after I yelled, he didn’t see the mouse or any evidence of one having been there,” she says. “And it got me to thinking about, what if you couldn’t convince your loved one that what you saw was real?”

This is her way, the creative burst from the mundane.

“Faithful Place” arose from seeing a battered blue suitcase in a dumpster outside an old house. “The Likeness,” her second book, was born from a throwaway bit of conversation in a Dublin pub.

French grew up with a love of mysteries, both in real and fictional life. Born in Vermont to David French, who worked for international non-governmental organizations, and Elena Hvostoff-Lombardi, a translator, the multilingual family bounced to Washington, Italy and Malawi before she settled in Ireland at 17.

She studied theater at college, joined Dublin’s Purple Heart Theater Company as a full-timer and fell in love with Anthony Breatnach. They were not exactly wealthy. She wrote “Woods” in the months-long lulls between castings.

An Irish publishing house offered her a modest advance. She thought she better check with an agent. She got big-time rep Darley Anderson in London to give it a look.

In a recent phone call, he recounts how he took the contract offer from about $22,000 for worldwide rights to about $220,000 for rights in the United Kingdom alone (for that and her next book).

“I don’t know how much she was making as an actress, but it couldn’t have been that much, because they had a rather large light bill and they weren’t sure how they were going to pay it,” he said, remembering their first conversations. “I think one of the reasons she says such nice things about me is because I got her a deal that allowed her to pay that bill.”

Today, things are different. She and Breatnach are married, have a 2-year-old daughter and her books are in airports.

Amy Costello, a pediatrician from Rockville, Md., plucked “Woods” out of an airport terminal bookstore last year. Hooked, she sent a copy to her daughter, Elizabeth, a student at the University of South Florida.

The pair were at the recent Washington, D.C. reading, with Elizabeth wrangling an evening off from work to make it.

“It’s really about her characters,” Elizabeth said. “I just don’t know how she writes such great male characters.”

French is busy signing a few feet away, her left hand looping out a signature, willing to reveal some, but not all, mysteries.