LOS ANGELES — The club was crammed, Three Days Grace were rocking the stage and a blonde on the shoulders of a dude in the front row was flashing devil horns.

It was a typical rock concert except for one small detail. The blonde was pop starlet Hilary Duff. And while the singer/actress has been listening to heavier music lately, she was actually at this show to work; her afternoon with Three Days Grace and several hundred extras was being captured for a scene in her upcoming movie "Heart of Summer" (see "Hilary Duff Can't Stay Away From Big Screen A Moment Longer").

"Basically what happens [before the concert scene] is my dad and my brother got in a big fight because my brother's fighting for me to go to this [performing arts] school because he knows that I'll do a great job there," Duff explained. "And he gets grounded ... and I had gotten tickets for his graduation present to this concert ... so we sneak out and we drive there and we go to the concert and we have a great time."

Sounds like another fluffy Duff movie, right? Not exactly. On the way home from the concert, her brother, played by Jason Ritter ("Freddy vs. Jason"), is killed by a drunk driver. Duff's character learns later that her brother had secretly signed her up to attend a summer session at the arts school in Los Angeles.

"She really wants to go to because she has a really great voice, but she has to kind of lie to her dad to get there and her aunt and her mom are in on it," Duff said. "But at the same time, she's like, 'I don't know if I should go because it's so soon after my brother dies.'

"She's just going through a lot of stuff and she's kinda the type of person that bottles it all in," she continued. "She has a very strict dad and he kind of wants everything his way. And her whole entire life, she's just gone along with it. ... Her brother's always been the type of person pushing to get out [of their small Arizona town]. And she's always just gone with the flow and now she wants out."

David Keith, who has played villains in dozens of movies (most recently "Daredevil"), plays Duff's father, while Rita Wilson ("Runaway Bride") plays her mom and Rebecca De Mornay ("Identity") plays her aunt. John Corbett ("My Big Fat Greek Wedding") and Oliver James ("What a Girl Wants") also co-star as a teacher at the school and Duff's love interest, respectively.

"This is my first step toward working on a more dramatic movie," said Duff, whose credits include "Cheaper by the Dozen," "Agent Cody Banks" and "The Lizzie McGuire Movie."

" 'A Cinderella Story,' which is the movie that comes out before ['Heart of Summer'], definitely has a little more edge to it," Duff explained. "[My character] deals a lot with her father dying and with not being accepted at school, but the movies are totally, totally different. It's a little more serious, it's a little more older.

"I'm not saying I totally wanna go there right now, though, you know," she added, smiling. That's because, at the moment, she was having too much fun going to a rock concert.

"It's really funny, because I have been on tour lately and people just want to touch your hand and they get so excited and I didn't know what that was like," she said. "I didn't know too much about Three Days Grace before we had started the filming, but I really love their music now. And it's funny to be on the other side, like 'Ahh,' screaming crazy, you know, being obsessed with somebody. It was a little awkward at first, but I got the hang of it."