Welcome, son of Boo.

Boo Radley, that is.

Boo -- for those of you don't watch black-and-white films -- was the man who saved Jem and Scout Finch from mean Bob Ewell in 1962's To Kill a Mockingbird. Boo wasn't too smart, and he didn't have many social skills. His family was so ashamed of him they kept him locked up in the house.

But the neighborhood kids knew he was in there and did their best to draw him out, if only to test each other's mettle. Little did they know Boo had appointed himself their guardian angel -- and that he watched over them even when they weren't paying much attention themselves.

Much has changed since 1962, and much has not. Karl Childers is emblematic of both.

Like Boo, Karl, the man-child of Sling Blade, spent his early years locked up, though for Karl it was in the woodshed behind the house. And Karl eventually got out, though not to a hero's welcome.

Karl (Billy Bob Thornton) was sent to a mental hospital for killing the local bully, whom he saw "having his way" with Karl's mother. Karl killed his mother as well, when she protested too much.

Unlike Boo, however, who has only a phantom presence until the last reel, Karl dominates Sling Blade from start to finish, whether he's telling the story of how he came to kill his mother and her lover or preparing himself to act as the guardian angel of his new-found family in the only way he knows how.

Thornton, who also scripted and directed the film, gives Karl a number of dimensions not available to the ghostly Boo.

Karl has a stiff upper lip that C. Aubrey Smith would have died for, and when he speaks, he speaks with authority, if monosyllabically, punctuating each utterances with an emphatic "Uh-huh."

To Thornton's credit, he's mastered the otherworldly posture of the victim of institutionalization, and yet he imbues that posture with both dignity and strength. In Karl's dangling arms, high-water trousers and protruberant shirt there is a comforting consistency that helps pull the disparate elements of the film together.

More importantly, Karl reveals -- one piece at a time -- a sinewy moral code that refuses to snap, even under pressure from the most aggressive of the local yahoos he meets after his release from the hospital.

That would be Doyle Hargraves (Dwight Yoakam), a redneck contractor who devotes his life to making life miserable for Karl's adopted family: single mom Linda Wheatley (Natalie Conerday); her son, Frank (Lucas Black II); and Linda's gay boss, Vaughn Cunningham (John Ritter).

Sling Blade is an elaboration of an earlier 25-minute film, Some Folks Call It a Sling Blade, and like many elaborations, it occasionally seems more extrapolated than plotted. Once in a while the logic is weak, and there are gaps in the motivation -- like why is Ms. Wheatley so quick to take in such an unusual outsider?

And yet, caught up in Thornton's masterful performance, we're inclined to overlook small sticking points and keep our eyes on the big picture.

Thornton has once again brought to life the American primitive -- the unlearned character whose goodness and common sense prevail over overwhelming odds -- and he gives Karl the kind of moral victory we all yearn for. Fortunately, we get to watch the battle from a safe distance.

Boo Radley offered talented newcomer Robert Duvall an unusual big-screen debut. We can only hope Karl Childers is as good to Billy Bob. Uh-huh.

[ by Miles O'Dometer ]