“I think you’ll learn a lot of history,” says a grim-faced dressmaker (black) to Mardi Gras queen Helen Meaher (white) early in The Order of Myths. Mobile, Alabama, has two separate Mardi Gras carnivals—one white, one black—and if Meaher is aware that her ancestors brought in the very last American slave shipment to Mobile in 1859 (including her black Mardi Gras counterpart’s ancestors), she’s not letting on. No one in the film admits to learning anything they haven’t known for years; Margaret Brown’s documentary zeroes in on the ways words like “culture” and “tradition” can become poisonous euphemisms—to wit, the defense for Mobile’s last true bastion of segregation. But Brown hasn’t made agit-prop or a heavy-handed exposé of the obvious (viz., Southern racism is alive and well, just more genteel and better-disguised). Quietly shocking, The Order of Myths is a deft, engrossing cross-section of Mobile life, heavy on local color and insight—from the old-fashioned debutante balls of the white Mardi Gras and the rowdier black dance, all the way down to the Mobile Mystics, a group of Larry the Cable Guy look-alikes whose idea of a proper greeting is throwing beer cans at their president.