Apart from some wicked accordion playing by Kevin Schramm, what's most engaging about the Mollys, separating them from many other roots-folk bands, is the dark, intelligent density of their original material. McCallion penned most of the songs on their latest album, Moon Over the Interstate: Her stories of working-class lives, souls slowly unraveling as a result of economic or spiritual strain, are instantly believable, witty, at times a bit angry, hinting at a punkish energy that never feels like hipsterism. (It was through catching both the Pogues and Los Lobos in Tucson that Zavala and McCallion figured out how to fuse their roots-music love with a rock & roll wildness.) Fans of Brave Combo and One Fell Swoop have at least two reasons to make the Mollys' first St. Louis gig: They're every bit as danceable as the first band, and the second will be opening.