TOKYO, Japan - John Verdon was 65 and retired, reading a lot of detective stories and talking about them with his wife, when one day she suggested he write one himself.
He took her up on the challenge, and Dave Gurney - a retired New York City homicide investigator just beginning his new life when mysterious letters start arriving - was born.
The book was snapped up by a publisher and came out in 2010 to rave reviews, and Gurney's adventures have continued with two more books, the latest - "Let the Devil Sleep" - just out.
Verdon, a former advertising executive who retired at 53 and turned to furniture making before writing, said he has been surprised and pleased by the results.
"When I wrote the first book I didn't even imagine it would be published. I had the time to do it, my wife encouraged me to do it, and I wrote the first one hoping she'd like it," he said, noting that the suggestion for more came from his agent.
"From that point on I think it kind of took hold of me, because during the course of finishing the first book I'd become close to and interested in the characters. So the idea of putting them in new situations and being with them again felt comfortable to me."
As the new book starts, Dave has fallen into a depression as the result of injuries suffered in his previous escapade, but the reappearance of a serial killer after a decade gradually rouses him to action.
Verdon, who said he'd always wanted to write but thought advertising was the only way he could write and make a living, said that one of the challenges of carrying on with a series is working to keep the reader interested.
"I've read both types of series - series about characters that don't seem to change at all, and then I've read others in which you grow old with the character and you watch their kids grow up and all that," he said.
"I think they have to change and I think that mechanism for change comes from the fairly horrendous things that happen toward the end of each book.
"When I started writing the third book, one of the things I had to deal with was to imagine: okay, here's a guy who's been shot three times a few months ago, where does that leave him?"
Despite bringing out a book a year, Verdon said he doesn't rely on a detailed outline but rather scribbles ideas down on index cards whenever and wherever inspiration strikes.
"I have two ballpoint pens in my pocket because God forbid I should be making a note and one of them should run out of ink. I have two pens and have a dozen index cards in the pocket of my shirt every day," he said.
Verdon then stuffs the cards in a manila envelope until the envelope starts to burst, at which point he takes out the cards, usually by then numbering four or five hundred, and arranges them on his dining room table until he starts to have a structure of acts and then of scenes.
"Eventually I sit down at the computer and start actually turning it into something that looks like a novel," Verdon said, noting that he is a "careful" worker who usually writes around two pages a day.
His advice for aspiring writers is simple: don't wait until you're 65 to start, the way he did, and stick with it.
"Over the years, when I was in the advertising business, I'd start a novel and I never got more than 50 pages into it before I lost interest," he said. "So once you start it, finish it."