Meet Heroes' new bad guy. Or is he?

The heroes of NBC's Heroes won't be vanquishing their newest nemesis any time soon: Prison Break's T-Bag, Robert Knepper, joins the cast for season four as carnival leader and superpowered bad guy Samuel—or is he?—and he told us that he has signed a contract to ensure he'll be menacing as long as possible. (Spoilers ahead!)

"I just became a series regular, so as far as I'm concerned, they're stuck with me till it ends," Knepper said in an exclusive interview Wednesday night in Pasadena, Calif., during the Television Critics Association summer press tour. "I started out as a recurring, so I could have [been] vanquished soon. Then they decided that they want to keep me—or they didn't want to lose me to something else—which is always a possibility in the business world of acting. So they kept me on, made me a slave to Heroes."

Viewers will meet Samuel in the season premiere, Knepper said. "I think when the lights go up, the first thing you'll see is me kind of doing something like this," Knepper said, mugging a wide-lipped grin and rocking back and forth. "Kind of a lilt, I don't know, some kind of an Irish lilt kind of thing."

And, at least at first, what Samuel wants will be pretty simple. "I think he wants to rule the world," Knepper said. "He sort of comes off as a guy who really cares about his own family, but I think we're going to find something. He seems to be drawing everybody in, all the heroes that we love, kind of a web. One by one he'll pull these guys in, and I think we'll find out a little bit more about them, and in the process discover what Samuel's motives really are."

Already, several episodes into the season, Samuel has encountered Hiro Nakamura (Masi Oka), Peter Petrelli (Milo Ventimiglia) and Sylar (Zachary Quinto). "My first episode I worked with Masi," Knepper said. "Then I worked with Milo, and I'm about to work with Zach."

The pending encounter with Quinto's character hints at his mysterious fate. Last year's season ended with Sylar taking the form of Nathan Petrelli (Adrian Pasdar), thinking he was Nathan but knowing something was off.

"This episode, he's not in his right mind, so he doesn't know quite who he is," Knepper said. "So he's like, 'Who are you? OK, I'm open to change.' It's one of those great things about writing, when the audience knows you to be the villain and then you suddenly have amnesia and you have no idea who you are. It's one of those little things."

In Prison Break, Knepper used a Southern accent to bring the odious T-Bag to life. For Heroes, he's trying out something new.

"Don't hold me to this, but right now he's either Irish, Scottish, one of the Beatles, Keith Richards or Liam Neeson," Knepper said. "I'm all over the place, but I have no idea yet. What I love about it is I'm sort of playing, and they're very forgiving. My dialect coach also doesn't know I'm working without him right now. I love Tim Monich, he's amazing, but I didn't have any time to call him. It figures. I get on the show, and half the crew is somewhere from the British Isles, like, 'Oh, no, you're going to hold me to this.'"

Heroes returns Sept. 21 at 8 p.m. ET/PT on NBC.

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