Adrian Pasdar, Heroes

As NBC's Heroes closes the book on its third season and the "Fugitives" volume (Monday at 9 pm/ET), Sen. Nathan Petrelli is on a mission to atone for what he's done: namely, making his friends fugitives in the first place. There's just one problem — the nearly invincible and now shape-shifting-enabled Sylar is standing in his way.

To make matters worse, Sylar is using his ability to live inside the skin of Nathan — all part of an effort to get close to the president and eventually impersonate him as well. But Pasdar said Nathan is fighting against himself just as much as he is Sylar.

"In the last four episodes, [Nathan's] been realizing what he's done, what overreaching ramifications his actions may have," Adrian Pasdar tells TVGuide.com. "There's been a quiet backing up into what the whole thing is really about, and a getting closer to seeing a redeeming light.

"Going into that last episode," Pasdar continues, "[Nathan's] really coming back with a definitive purpose and he's putting a face on the bad guy. And of course, with Sylar being that guy, he's confronting the own worst part of himself manifested in somebody else."

Sounds complicated, right? It is, but the showdown does provide one of the most interesting plot twists the show has explored since its first-season glory. Pasdar described the unexpected direction as a new beginning for the show.

"The nature of TV is to be drawn out and serialized with a lot of repetition and redundancy, but the [finale] is a chance to end that and move on to something new in whatever way it wants to re-imagine itself," he said. "It's kind of wild — and it's probably the best thing that could have happened to our show."

With all the shape-shifting, one of the trickiest parts of the finale is keeping up with just who exactly is on screen at any given moment. Even so, Pasdar said he enjoyed playing Nathan and Sylar-as-Nathan equally.

"When they wrote the part, everybody — from craft services on up — had an opinion of how I should play Sylar," Pasdar said. "I studied a lot of [Zachary Quinto's] mannerisms, his moves, the way he talks, his cadence. But in theoretical terms, playing Dr. Jekyll and Mr. Hyde is a lot more fun than just Hyde or Jekyll. Being able to play both takes the onus off of either. You don't need a balancing point for your behavior, you can just be. It's a lot of fun for the writers and for me."

We won't spill the beans on just who comes out on top in this season-ending tête-à-tête (though we will say that not much is what it seems), but Pasdar said he's looking forward to what the next volume, "Redemption," has in store for Nathan and the other members of the Petrelli family.

"The best TV is always about family, whether it's All in the Family, or The Sopranos or The Flintstones. And at the end of the day, Heroes is about family," Pasdar said. "Sibling rivalry was brought up kind of early and felt kind of tired, so what's fun about this is that [Nathan and Peter] are confronting each other but ultimately coming together to fix a problem that we both had a hand in. I have an idea where it's headed, and it's right to the core of family. The next step is really interesting."