Knepper, fresh from playing malevolent prison escapee Theodore ``T-Bag'' Bagwell for four seasons in the cult thriller Prison Break, is about to take on a potentially even more dastardly role in Heroes, now entering its fourth season.

Knepper plays the serial thriller's new villain, Samuel Sullivan, the mysterious leader of a travelling carnival that has become home to those people with special abilities who, for whatever reason, are reluctant to deal with the outside world. Samuel, as Knepper's character will become known, is a kind of Mr. Dark in a Heroes season that, on the face of it, will echo the darker, more mysterious elements of the Ray Bradbury classic Something Wicked This Way Comes.

Knepper, a career actor who cut his teeth on the theatrical stage in his hometown of Fremont, Ohio before majoring in drama at Chicago's Northwestern University, is often typecast as a villain, but he approaches each new role as if he were playing the sweetest person in the world.

``I have a good vibe for Heroes, because I'm pulling my hair out trying to discover that character,'' Knepper told Canwest News Service in an interview. ``The difference between now and Prison Break is that Prison Break put me on the map. With Heroes - it's weird, but I haven't talked about this before - it's almost as if I feel the audience will be watching me develop the character as I'm developing it. I haven't got it all developed ahead of time. I'm still fiddling with it. We'll get to see what happens with it from one week to the next. For the audience, it's like the theatre. It's like watching a live performance unfold that happens to be on film.''

Samuel is charming, Knepper said. Charismatic.

``He's going to draw you in. He's going to draw all these heroes' stories out of them.''

Samuel is also looking to reclaim a part of his soul, Knepper said. Samuel isn't a villain, really. He's a hero who's misunderstood.

``Hopefully, you'll get a gleam of light into his life as well.''

T-Bag wasn't a villain, either. Not really. He just wanted his slice of the pie, his cut. Is that so bad?

Knepper knows he can be a ferocious presence on the screen, with his intense face and just-watch-me magnetism, but he's not about to steal the spotlight.

``I'm an ensemble guy,'' Knepper said, hearkening back to his stage training. ``My whole life, I've been an ensemble guy, because I grew up in the theatre. Anything I can do to help tell the story as a whole - that's who I am. And I always will be.''

Knepper feels added pressure playing such a prominent role in Heroes, because it is one of the most widely seen TV series.

Knepper travelled extensively while promoting Prison Break, and he would see the same DVD box sets of the same four TV series in video stores wherever he went, whether it was Malaysia or Madagascar. Prison Break was one. Lost and 24 were others. Heroes was the fourth. That's testament to how far-reaching Heroes really is, Knepper says.

Knepper admits he didn't have time to watch Heroes while he was making Prison Break, but he caught up with the early episodes once Prison Break ended.

``It's an a-ma-z-i-n-g pilot episode,'' Knepper said. ``It's unbelievable to watch. It's sexy. It's scary. All pilots are good - otherwise they wouldn't be picked up. Every once in a while, the shows that follow that are also great. Prison Break was one of those, especially that first year. Heroes is another, and I'm very happy to be doing this. I have a simple rule in life: If I like the character, I want to do it.''

Knepper says he learned some valuable lessons while making Prison Break.

``Prison Break taught me that the writers have to break the story. They ponder it, they wrestle with it and all of a sudden they figure it out. What I realized, week after week after week of doing Prison Break, is that you do the same thing as an actor. You break the story from that character's point of view. You break that scene down and go, `Ah-a, I get it.' It's kind of like a slow- moving river that's coming to a waterfall, and all of a sudden the water starts to flow. You can't just memorize a scene without knowing what the scene's about. If the writing's not good, I can't memorize it at all. I'm like, `Damn, why won't these words stick in my head?' Once I break the scene, like the writers do, then it flows.''

So far, Heroes has been both a challenge and a reward, Knepper says.

``What I'm doing is not radically different from what I've done before. Maybe, after one year of being on the show, then I'll have it figured out; I'll know exactly what it is. But, right now, I love the challenge. I love the craziness of not knowing what's coming next.''