BRENTWOOD, Calif. — Greg Kinnear said he first heard about it in geometry class.

A high school buddy whispered something about the guy from "Hogan's Heroes" having a secret life that involved sex, murder and videotapes.

"I didn't believe it," said Kinnear, casually dressed in jeans and sipping tea in a Brentwood restaurant. "It just didn't make sense. I thought he got it wrong.

"How could this guy — this smiling, affable, charming guy from a lovable sitcom, who was practically an all-American brand, like Coca-Cola — get so messed up? I just didn't understand all the contradictions."

It wasn't until years later — when he was offered the chance to portray the smiling but depraved Bob Crane in director Paul Schrader's dark tale of the late actor's double life in "Auto Focus" — that Kinnear started to understand.

"Bob Crane is the poster child for addiction," the actor said. "It wasn't crack or alcohol; it was sex, which people think of as normal and a good thing. But, his attitude toward sex was anything but normal. It was compulsive, and compulsive behavior is what addiction is all about."

For six seasons, Crane starred as the clever Col. Hogan, head of a daring band of World War II operatives working from inside a Nazi prisoner-of-war camp. Off camera, when he wasn't making audiences laugh, he seemed to be the perfect family man.

But, as it turned out, he had an unnatural attraction to sex, and to the documentation of that sex. When he was murdered by an unknown assailant in an Arizona motel room in 1978, police found a vast collection of pornographic photos and videos, most of which he had shot of his own sexual encounters with hundreds of women.

"If someone were going around Hollywood pitching an idea for a fictional story about a beloved actor living this kind of a double life, no one would buy it," Kinnear said. "Here was a guy living this ideal family life while oblivious to the damage he was doing to himself, his relationships and his family because of his addiction. And, the amazing thing is that it's a true story."

Kinnear, 39, said Schrader, who wrote "Taxi Driver" and "Raging Bull" and directed "Hardcore," was the right director to handle this type of material.

"Paul is as abrupt as a freight train. He is straightforward and doesn't dance around issues. That is what this story needed; it wouldn't have worked with a timid director.

"Because it was Paul and not some timid director, the movie's really good at not trying to say too much," Kinnear said. "Too many of these biographical movies end up being a morality tale where we see the protagonist thinking about his decline and searching for answers.

"We couldn't go in that direction because Bob never seemed to do that. The uniqueness of this film is that we have this clueless guy who remains clueless throughout the story. You can almost hear the audience warning him of his mistakes, and he refuses to listen.

"That is very much the story of Bob Crane, who was taking these decidedly dangerous steps into a lifestyle that was undermining his work and his family, and yet he didn't seem to hear the bells that were ringing pretty clearly all around him.

"It's a fascinating story, and hard to believe that it's true."

Born in Indiana, the son of a State Department official, Kinnear moved often with his family, settling in Beirut, Lebanon, when he was about to enter the seventh grade. Nine months later, civil war broke out, and the family relocated to Greece, where they stayed for six years.

After graduating from high school at the American Community School in Athens, where English was spoken and most of the students were the children of American diplomats or from wealthy European families, Kinnear enrolled at the University of Arizona.

Although he was amused by his fellow students' fascination with their newfound freedom to consume large quantities of beer — there was no drinking age in Greece — Kinnear said he had no trouble fitting in.

"The odd thing about moving around so much as a kid is that you learn to adapt pretty easily," he said.

He graduated as a broadcast journalism major with hopes of a career in news, but those good looks, charm and sarcastic wit steered him in another direction.

Kinnear, after a brief fling in the world of movie marketing, wound up smirking his way through a three-year stint on the cable show "Talk Soup." That led to "Later With Greg Kinnear," which segued into a role as a talk-show host in the Damon Wayans movie "Blankman."

Director Sydney Pollack, apparently ignoring "Blankman," liked Kinnear's work on "Talk Soup" and cast him in his remake of "Sabrina."

Despite never having an acting lesson, Kinnear's movie career took off. In only his fourth role, in "As Good As It Gets," he was nominated for an Oscar for Best Supporting Actor. He has made 15 movies in a seven-year acting career.

With the exception of "As Good As It Gets" and the Mel Gibson war film "We Were Soldiers," it seemed as if Kinnear might get typecast as the glib friend who never gets the girl ("Loser," "Someone Like You"). In another time, it was called the "Gig Young Role," after the actor who always seemed to lose the girl to the leading man.

"Auto Focus" should change that kind of typecasting forever.

"It is not lost on me that this movie is different than anything I've done," Kinnear said, adding that he has heard that writers Larry Karaszewski and Scott Alexander picked him because he looks so much like the real Bob Crane, and also because they read that he was looking for more challenging roles.

"But that is not how I saw it in the beginning. I saw it as an extension of the roles I've played before. It wasn't until people kept mentioning how much of a risk it was that it began to dawn on me that it was a departure for me, and perhaps a little risky.

"Believe me, I am aware of the perceptions some people have of me. They remember me from TV, when I was just playing me. Now, I'm playing characters, and I'm pleased with my work so far. And I'm pleased with my work in this movie. People should know that I'm not playing me in this movie. I'm playing a character. We may look alike, but Bob Crane and I are completely different people."