Robert Knepper is 'Heroes' regular

Character at the center of new circus story line

"Heroes" is getting more villainous: Robert Knepper has been upped to regular on the NBC drama.

Knepper's character Samuel is at the center of the major new story line on the sci-fi series. He is the charismatic but evil Earth-moving ringleader of a traveling carnival who recruits people with special powers for a mysterious purpose.

"Prison Break" alum Knepper originally signed for six episodes and so far has appeared in every episode of the show's upcoming fourth season. Knepper, who recently joined the cast of "Heroes" for the series' panel at Comic-Con in San Diego, follows in the footsteps of another baddie on the show, Zachary Quinto (Sylar), who also started off as a recurring before becoming one of the show's breakout stars.

Knepper is repped by Fortitude, D/F Management and attorney Todd Rubenstein.