When we last saw Matt Parkman on Heroes, he had used his psychic powers to help vanquish Sylar. The preview of Vol. 5 suggested that Sylar is already starting to emerge from the body of Nathan Petrelli, despite Parkman's best efforts. As season four, Vol. 5 continues, Sylar lingers on in Parkman's mind, too, said actor Greg Grunberg.

(Warning: Spoilers ahead.)

"When we come back in season four, you see that this transfer of brains or whatever didn't go smoothly, and remnants of Sylar are left behind in me," Grunberg said in an exclusive interview on Aug. 5 in Pasadena, Calif., as part of the Television Critics Association fall press tour. "He's in my subconscious and I can't control him. Then he starts to control me, which is very, very cool."

Sylar's already got Nathan's body. Does he get Parkman's, too? "Well, he's in my head," Grunberg explained. "No one else can see him but me, so he's in scenes with me. It's very cool."

Zachary Quinto continues to play Sylar, in Parkman's vision of Sylar's presence. Grunberg also revealed some of Sylar's dirty deeds. "[He] kidnaps my child to get his body back. It's that kind of stuff, and it's very personal and much more relatable, I think."

That must mean Sylar uses Nathan's body to kidnap Parkman's daughter, right? No, said Grunberg. That's a separate thing while Sylar plays the brain game with Parkman. Don't worry about following the complicated storyline. Grunberg said it all makes sense.

"It's very easy to follow, actually, my storyline," Grunberg said. "It's cool how it's done. I love it because it's more character-based. The show became all about saving the world, and it's very abstract. It's kind of hard to grasp that. What does that mean? It's very spectacular, and it's fun, but then if you do it every week, it doesn't mean anything. And if everybody has powers, it doesn't mean anything. So this year it's kind of getting back to season one, where it's all about the characters just wanting to be real and normal. I don't want this power, I don't use it, and I'm forced to use it because Sylar's doing anything [he can]."

Grunberg has been enjoying the team-up with Quinto so much that he hopes Sylar never gets out of Parkman's head. "I went to the writers, I was talking to them tonight, and I was like, 'Guys, please don't end this. Don't resolve this, because we're having so much fun.' What's cool is that my powers evolve, and I start this year so regretting what I did last year that I have absolutely cut it cold turkey. I refuse to use my powers, and Sylar wants me to, so he's constantly on my shoulder going, 'Use your powers, you p-ssy.' It's great. It's really cool."

Too bad Parkman doesn't have a good angel on his shoulder telling him not to listen to Sylar. "No, that's me, but I'm not strong enough. It's pretty great."

Heroes returns Sept. 21 at 8 p.m. on NBC.