With the stunning success of "The Fast and the Furious," he exploded on the Hollywood scene. "XXX" only intensified the heat surrounding him.

Movie industry insiders were speculating that he could be the next Arnold Schwarzenegger — when that really meant something. After he made the breakout comedy "The Pacifier," in a career shift that was reminiscent of Schwarzenegger's "Kindergarten Cop," people were convinced that he was new Arnold.

Now, he's starring in a Sidney Lumet courtroom drama called "Find Me Guilty," which opened in New York and Los Angeles last weekend, and nobody knows what to make of Vin Diesel.

California's governor never worked with someone of Lumet's stature. With five Oscar nominations and a resume that includes "12 Angry Men," "Dog Day Afternoon," "Network," "The Verdict" and "Serpico," Lumet is an old-school Hollywood director with distinction.

He's worked twice with Al Pacino, for crying out loud.

Which begs the question: What's a classy director like Sidney Lumet doing in the same movie as Vin Diesel, the tough-talking, muscled action star with the shaved head?

Well, you'd be surprised. In fact, a lot of people are going to be surprised.

Diesel, 38, says this is the role that will show people that he is more than the sum of his action parts. In the film, he plays the real-life New Jersey gangster who defended himself during the longest mob trial in history. Diesel even wears a hairpiece in the role, just like a serious actor.

During a 2002 interview, Diesel was fresh off one of his action triumphs — and he literally swaggered around his hotel suite, making jokes, talking loudly and playing to his entourage. This time, he was alone in a Los Angeles hotel room, speaking softly and thoughtfully, but still displaying flashes of his characteristic self-confidence.

Q. You're feeling pretty special, aren't you?

A. I do feel special. I feel lucky. And I feel validated.

Q. Validated?

A. A huge sense of validation working with Sidney Lumet. He's a huge, huge idol of mine. I used to watch his movies and stare at his actors. Did you know he worked with Marlon Brando in "The Fugitive Kind?" It's mind-boggling.

Q. Describe working with him.

A. The most amazing thing was when he would spit out an anecdote about the past but reference it to me.

Q. Explain.

A. The night before filming started, I was on the phone with him and I was a little insecure about whether I could be this guy. And he said, "Several decades back, I was doing this film called 'Dog Day Afternoon' with a young actor named Al Pacino. The night before we started shooting, he called and said he wasn't sure he could be this character who robs a bank to finance his lover's sex-change operation."

Q. Were there any insecurities about measuring up to his standards?

A. I had a huge insecurity. Not in the acting, but in the look. I couldn't wrap my head around playing a character who was 15 years older and so much heavier. I just didn't know how that would play out.

Q. How did you finally wrap your head around it?

A. The role came to me while I was doing "The Pacifier," and as long as I was doing something so safe as a Disney family comedy, I felt I could afford to play someone this different.

Q. The last time we spoke, you said you had higher ambitions for your acting career than just action flicks. Is this the movie you were talking about?

A. This is exactly the movie I was talking about.

Q. You don't think your career suffered a dip after you turned down the sequel to "XXX?"

A. Not at all. Movies like "Knockaround Guys" and "A Man Apart" were made before "XXX," and released later to take advantage of my popularity.

Q. Do you plan to continue doing action movies?

A. Yes, but the irony is that I have prepared my whole life to do Sidney Lumet films, not "XXX." My idea of success was always a Sidney Lumet picture. Or a Martin Scorsese picture. Or a Steven Spielberg picture. I wasn't necessarily thinking about a huge action franchise.