Though he avoids platitudes, David Cronenberg is a troubled moralist who lingers over cherished mythologies to find their dark residue: this masterpiece, an art film deftly masquerading as a thriller, seems to celebrate small-town pastoralism and critique big-city violence, but this position turns out to be double-edged. Josh Olson adapted his script from a graphic novel, yet the story develops with a subtlety that's entirely cinematic; two contrasting sex scenes between the hero (Viggo Mortensen) and his wife (Maria Bello), added by Cronenberg, are especially masterful. With Ed Harris, William Hurt, and Ashton Holmes. R, 96 min. River East 21.