Writer-director David Koepp says "Secret Window" "is so much up my alley. I like stuff that's set in your home base, and then the world starts to turn on you and you don't feel safe anymore." Click photo for larger image.

Writer-director David Koepp liked the challenge of bringing "Secret Window" to the screen, even though Stephen King stories have a poor track record when adapted for the movies.

"What attracted me is that it's kind of uncinematic," Koepp said this week on the telephone. "So much of it is about a guy's thoughts. It's almost impossible to get that on film. I kind of liked that aspect of being constrained. It's basically one location, a guy alone. It forces you into a thinking process with new ideas."

The movie stars Johnny Depp as writer Mort Rainey, whose marriage is breaking up. He takes refuge in his house in the woods (the actual location is north of Montreal), but he spends more of his time dozing than writing. He is shaken from his stupor when a stranger with a broad Southern accent accuses Mort of plagiarism and demands that he "make it right." Before long, Mort's family and acquaintances become the target of violent acts.

The character's paranoia becomes a key element of the film, but because we can't go into his mind the way a novel can, "You have to externalize a lot of things," Koepp said. "In the book, he never goes to a private investigator."

Also, he said, "This way, he has someone to talk to."

This kind of film all but cries out for the talents of Johnny Depp, who has made a career of playing unorthodox characters.

"He comes to the set with great ideas, and they're not what you expect. At first, you think he's kidding. Then you say, 'Let me think about it.' That's what makes his characters accessible."

For example, Depp suggested that Mort wear braces throughout the movie. Koepp thought that would be too much but used the idea in the film's final sequences.

"Here's my favorite," Koepp said. "The script has 14 pages of phone calls. That's dull. You have to find new ways to do it. There's a phone call with Charles Dutton [he plays the private eye], and I was out of ideas. [Depp] said, 'Well, my character has just driven up from New York, I've been in the car a long time, I've got to pee."

And so Depp grabs the phone, takes it into the bathroom and does his business as the camera cuts back and forth between him and Dutton, relaxing in a motel room half dressed.

Now that's naturalism.

Primarily a screenwriter, Koepp has directed three films. In each case, he adapted the screenplay from someone else's work. His original scripts, including "Panic Room" and "Spider-Man," went to other directors. Most of the time, he's not the one who gets to decide.

"I'd like to write a special-effects movie, but I would never want to direct it," he said.

But "Secret Window," he said, "is so much up my alley. I like stuff that's set in your home base, and then the world starts to turn on you and you don't feel safe anymore."

In the case of "Secret Window," that leads to an inevitable question: If Mort's so scared of what he might find at his isolated house in the woods, why doesn't he just go somewhere else? Preferably someplace with lots of people around?

"There are certain things you have to accept or there wouldn't be a movie," Koepp admitted. "But with Mort, there is also the factor that this is his ground. He may think, 'I've had this taken away. Why should I go anywhere?' "

Koepp says he enjoys writing original screenplays but slightly prefers adapting someone else's work.

"You get the benefit of someone else's thought. Directing is interpreting -- you have to attack the material. That's hard for me to do when I've also written it. You're missing a voice. Movies need more than one voice."

The advantage of the other voice being Stephen King's is that he has the right to approve everything about a movie, "but he doesn't use it. He just wants to have an emergency brake if the train is about to leave the tracks. Other than that, he wants you to make your movie."