Maybe Charlize Theron is onto something. Whenever this glamorous South African blonde goes ugly to play American salt-of-the-earth types, the Academy bestows a nomination (2005’s “North Country”) or an award (2003’s “Monster”) on her. As the producer and co-star of the Sundance Film Festival entry “Sleepwalking,” Ms. Theron has chosen to cast herself in another role straight out of a country-western song. But what at first glance might seem like mere mining for more Oscar gold is perhaps something deeper, as the film echoes a family tragedy from the actress-producer’s own past.

Ms. Theron plays Joleen, an irresponsible single mother who suddenly finds herself and her daughter Tara (AnnaSophia Robb) homeless when the police bust her live-in boyfriend’s marijuana distribution operation. While a reasonable person might take this as a wakeup call, Joleen insists that things are just dandy, thank you. Her trusting brother James (Nick Stahl) has a dilapidated apartment

where she and Tara can crash. But it only takes a day before Joleen has found herself a one-night stand and vanishes altogether, leaving Tara in poor James’s care.

James doesn’t exactly have it together, either. Habitually late for work, he soon finds himself out of both a job and a place to live. His former co-worker, Randall (Woody Harrelson), takes him in temporarily while Tara is in the custody of the local child protective services agency. But when James visits Tara at the foster care center and meets the mean girls with whom she has to bunk, he decides they both need to get away.

Hapless James couldn’t pay rent, but he apparently has enough for gas, food, and lodging until the pair reaches their destination: the family farm where Joleen and James grew up and from which they subsequently fled. We learn that their father, Mr. Reedy (Dennis Hopper), is the monster who single-handedly ruined all of their lives. He hasn’t changed much, and the martinet immediately puts his son and the granddaughter he’s never known to hard labor.

Screenwriter Zac Stanford, who previously scripted the 2005 Sundance hit “The Chumscrubber,” has come up with an interesting premise about a man who finally leaves his abusive upbringing behind by growing a backbone. In real life, Ms. Theron grew up on a farm and witnessed her mother kill her father in self-defense, so one can easily see why this particular story might resonate with her.

A traumatic childhood can leave emotional scars that take a lifetime to heal, and the cycle of domestic abuse can stretch on for generations. All of it can make engrossing subject matter for a film that seeks to explore the complexity of why some want to abuse and others allow themselves to be abused. But “Sleepwalking” doesn’t have the depth to pull it off, taking the Hollywood “psychology for dummies” shortcut and unloading the blame entirely on the head of the one-dimensional bogeyman. It’s a good thing the film is set in Northern California rather than North Carolina, because the only remaining cliché would be for the characters to deliver their lines with a thick Southern drawl.

Mr. Stanford’s screenplay often comes off as insincere, not only because it oversimplifies the causes and effects of domestic abuse, but because he glosses over the poverty factor. When the film’s cathartic ending suddenly turns hopeful, one might wish real life could be this easily manipulated.