Ten years and 800,000 words ago, Justin Cronin, at the time a well-regarded, if largely unknown, author of literary fiction and a recipient of the PEN/Hemingway Award, started telling a story—one that he didn’t think would be published.

“It began as a game,” Cronin recalls. “My eight-year-old daughter, Iris, challenged me to write about a girl who saves the world.”

Cronin and his daughter spent much of the next autumn wandering the streets of their Houston neighborhood, she on her bike, him jogging alongside, spinning out a tale that had only two inviolable rules. The first: everything in their story had to be interesting. The second?

Cronin smiles. “It had to have one character with red hair,” he says, adding “you don’t have to guess what color hair my daughter has.”

That story eventually became The Passage, a landmark work of supernatural fiction that not only topped bestseller lists nationwide, but transcended the genre, and was named one of Time magazine’s Books of the Year in 2010. In the second volume of the Passage trilogy, The Twelve, Cronin expanded on his success.

Now, with the publication of The City of Mirrors, the saga’s final volume (one that has already garnered intense pre-publication praise, including starred reviews from Publishers Weekly and Library Journal), the journey is ending not just for the characters readers have come to know and love (Peter, Alicia, Amy, and others), but for the author himself.

“Ten years is a long time in the real world,” Cronin notes. “Time enough for children to grow up.” His daughter Iris—the little girl who started telling tales of the Passage with him—is off to college, the bicycle she rode around Houston replaced by a slightly battered Mini Cooper. His son, a preschooler when the story began, is now taller than his wife.

“The world grows,” Cronin notes wistfully. “The Passage trilogy began in one phase of my life; it ends in another.”

Cronin will sign books at the Penguin Random House booth (2433) today, 10-11 a.m.

This article appeared in the May 13, 2016 edition of PW BEA Show Daily.