Poster girl Jessica Alba plays a less-angelic role

Frank Miller has always been known for his dark comic images. But he may get a new reputation when the poster for the film adaptation of his "Sin City" hits theater showcases.

Already, the poster is selling well on the Internet, where teen boys are finding Miller’s twisted graphic novel more accessible, thanks to Jessica Alba.

Alba, former star of TV’s "Dark Angel," plays stripper Nancy Callahan, who is kidnapped by a psycho and must be rescued by a retiring cop played by Bruce Willis. The film is due in theaters April 1.

"I had no idea that the comic was so dark until I started reading the script," says Alba, 23. "I thought, ‘Wow, this is so deep. I want to explore that dark side of acting.’ "

Which is all fine and good until you see the poster, which doesn’t show Alba’s dark side so much as her sexy side.

"I was pretty surprised when I saw it," she says. "They just took a shot from the movie. But I do play a stripper, so it’s accurate."