There are plenty of fierce battles in the new thriller "28 Days Later." Not all of them took place in front of the cameras. A terrifying story of a violence-inducing virus run amok, the new film from "Trainspotting" director Danny Boyle is the product of a spirited debate over the movie's soul. Is "28 Days Later" a mainstream scary movie? Or a highbrow art film that happens to overflow with zombies? If Boyle and his collaborators have made their decisions correctly, the answer could be that the film ends up being both things at the same time.