MURDER AND MANNERS.('The Little Friend')

Donna Tartt's languidly atmospheric new novel, "The Little Friend" (Knopf; $26), looks as if it's going to be a mystery: it follows the search for the killer of nine-year-old Robin Cleve Dufresnes, who was found hanging from a tree in his back yard on Mother's Day. But if you're startled when you finally learn the secret of the title, it isn't because this information comes as a surprise but because, by the time you get to page 543, you're so engrossed in just about everything but the murder that you no longer care who dunnit. And, by that point, you suspect that Tartt doesn't care, either. Like her best-selling 1992 debut, "The Secret History," this long-awaited second novel takes the shape of a murder mystery, but it's not really about a death at all. It's about a way of life.

Tartt, who was born in Mississippi, has set her new book in her home state, in a shabby riverside town called Alexandria. From the start, it's clear that the corruptions that interest her most are the familiar ones: ingrained, almost casual racism; hostility between the white-trash "plain people" and the "town folk" like Robin's maternal relatives, the Cleves, with their faded aristocratic pretensions; and--inevitably, in the literature of the South--the stranglehold of the past.

Twelve years after Robin's death, his murder remains unsolved, and the lack of resolution has created an emotional and moral limbo for his family. His father, Dix, has fled to Tennessee, where he lives openly with a mistress; the abandoned mother, Charlotte, floats around her disorderly house in a tranquillized fog, barely aware of her two surviving children, Allison and Harriet, who vaguely disappoint her for not being more like their brother. Allison, now sixteen, witnessed her brother's murder but can't recall what she saw, and spends most of her days sleeping. Tartt self-consciously invokes the Southern-gothic tradition to remind you that murder can make ghosts of the living as well as of the dead: Charlotte is compared to "some woman in a ghost story"; another character once discovered that her cat was being eaten alive by maggots.

Only Tartt's heroine, the ferociously independent and bookish twelve-year-old Harriet, who was too young to have known her brother, seems to resent the "forgetful doze" that has settled over her troubled house. After being told in her Baptist Sunday school that everyone ought to have a plan ("John the Baptist had a goal"), Harriet--the kind of girl whose idea of fun is to see how long she can subsist on eighteen peanuts a day, "the Confederate ration at the end of the war"--sets out to find her brother's killer.

The bulk of "The Little Friend," which is divided into seven long sections, is devoted to Harriet's implacable pursuit of the man she believes to be guilty, a young redneck named Danny Ratliff. A former classmate of Robin's, Danny apparently once "confessed" to the killing, in a moment of confused childish braggadocio. But Harriet's quest for vengeance, in which she is loyally assisted by her best friend and frequent partner in mischief, an eleven-year-old boy named Hely, goes horribly wrong. Tartt's book is, among other things, a dark coming-of-age story: the slow workings of the plot, which interweaves the Cleves' history with that of the Ratliffs, force Harriet to recognize that nothing is what it seems, least of all herself. In her naive prosecution of Danny, Harriet racks up a rap sheet--forgery, breaking and entering, assault, conspiracy, and attempted murder--that makes it increasingly difficult to distinguish victims from perpetrators. Indeed, Tartt has constructed her narrative so that the Ratliffs and the Cleves are mirror images of each other: the former a family of orphaned boys being reared by their backwoods grandmother, Gum; the latter a family of neglected girls being reared by their formidably crisp grandmother, Edie. Danny, finally, doesn't seem that different from Harriet.

If Harriet's plans become gratuitously elaborate--at one point she steals a deadly cobra and hurls it from an overpass into a speeding Trans Am--so do the nearly five ...