If Karl's life were a series of books, it would be bookended by his stay at the local mental hospital. The film opens there, and it ends there. When it opens, it looks bleak. Its residents shuffle around in drab clothing. The walls are plain. It's quiet. Being there would drive us crazy instead of helping us recover our mental health.
But we weren't raised isolated from society, sleeping in a shed as Karl was. To Karl, the mental hospital might as well be the Four Seasons. He can read whenever he wants, he gets a variety of meals (although they must not serve biscuits, which should be a crime), and the lighting is fantastic. The hospital is his home, and Karl wants to return there at the end of the film because he's homesick.
Small Town Boy
Karl's life is just like the John Mellencamp song "Small Town." Karl was born in a small town. And he lives in a small town. Well, in a mental institution near a small town, but stick with us. His parents live in the same small town—well, the parent he didn't murder, anyway.
Karl's job is so small town, it provides little opportunity. But considering Karl has had zero opportunity for his entire life, little opportunity is a big upgrade.
Karl was educated in a small town. He was taught the fear of Jesus in a small town—which, frankly, really screwed him up. And he'll probably die in a small town, or back in the mental institution near that small town.
Millsburg, Arkansas is a small place, but it fits Karl, who has small thoughts and small dreams. We're not insulting him. It's true. The man's biggest pleasure in life is a cardboard tray of French fries. And he likes it that way.
The town has a few interesting places within it—like the mental hospital, where Karl is institutionalized. It's somewhere within short driving distance of Millsburg, and it's used to misdirect us as we rely on our preconceived notions of mental hospitals being dangerous places. When Karl is interviewed about the crime he committed, he's lit as if he's Hannibal Lecter. Out in town, though, we learn that Karl is much gentler than that sadistic cannibal.
Another significant place in Millsburg is Frank's "secret place." It's a little clearing in the woods, near a river, where Frank goes when he wants to be alone. The more Doyle is around, the more Frank wants to be alone. Frank shows Karl how much he trusts him by bringing him to the secret place.
It's in that secret place that Frank and Karl share their innermost thoughts. They talk about Doyle, about Karl's crime, about Karl's dead brother, about violence, murder, and suicide. It's heavy stuff.
It's also an unusual place for Karl to be. He's never been a man to have that much private space to himself. He grew up in a shack, after all, and he was raised, for lack of a better word, in a mental hospital. The secret place is like the whole wide world to Karl—it's big, and the thoughts his thinks there are scary. Frank is comfortable going to that place, but in the end, Karl decides to leave it and keep his secrets to himself.