04/24/2010 05:12 am ET | Updated May 25, 2011

Dennis Lehane and His Dream Island

Dennis Lehane gets ideas for novels all the time. But here's the key question: Once you've had the idea, can you sustain it?

"If I come up with 40 good ideas, out of that I might be able to execute one," the 44-year-old novelist says by telephone. "Once you get into the second act, then you know if you can sustain it. That's where the trouble lies. That's the valley of darkness.

"They say if you put a monkey in a room with a typewriter, he'd eventually come up with a good idea. But then you've got to execute it. You don't know until you let it play out. It's like a spool of yarn that you push and see if it will go the distance - or will it run out before it gets across the room? That's the way it is for me. I get a lot of ideas - and most of them suck."

One idea that obviously didn't suck was the one he had for Shutter Island, his best-selling 2003 novel that's been made into a box-office-topping film by Martin Scorsese. The movie, released last Friday (2.19.10), took in more than $40 million in its first weekend.

"That idea came from a confluence of things," Lehane says. "The initial kernel of an idea was a place. I was walking down the beach and the idea of an island with a mental institution popped into my head.

"Then, a couple of weeks later, I came home late one night after an exceptionally tense day, one where I'd gotten some particularly bad news. I fell asleep in my chair - and then I woke up an hour later and scribbled down the plot. When I woke up the next morning, there was the entire plot of the book. It wasn't like I'd had some classic dream. I just popped awake with the whole thing in my head. I definitely think in a large way it was connected to the level of stress I'd had that day. Those 'poof' moments happen once in a lifetime."

Shutter Island is the story of U.S. Marshal Teddy Daniels (played in the film by Leonardo DiCaprio), assigned a case that takes him to an island asylum for the criminally insane, where he must help find a patient who has vanished. It's set in 1954, but Lehane works in modern-day paranoia about mind-control, torture, government oversight and the invasion of privacy.

That came from his own feelings about what was happening in post-9/11 America, as the Bush administration turned the war on terrorism into a frontal assault on civil liberties, Lehane says.

"I think there was a lot of propaganda going on in the country when I was writing it," he recalls.