What you’ve probably heard about Mud, if you’ve heard anything, is that it’s one in a recent series of movies showing a different side of Matthew McConaughey. This is true enough, and reasonable enough: In Mud, the title character is played by McConaughey, and the story’s reason for being is his striking presence.

But what’s truly impressive about this too-minimally distributed film — the third feature from highly adept yet still largely unknown writer-director Jeff Nichols — is a powerful, understated performance by 17-year-old Tye Sheridan as its proper protagonist. Sheridan plays a rural teenager who, along with his best pal (Jacob Lofland, also great), discovers a fugitive (McConaughey) hiding out on an island in the Mississippi River. The mysterious and charismatic Mud becomes a dubious father figure for the boy, who is busy learning to navigate a breaking home and a breaking heart.

With hints of Huck Finn and plenty of precocious wisdom and originality, Sheridan transmutes coming-of-age concepts into lived experience. You know this kind of actor: The less he says, the more truth he conveys. A movie in part about crumbling codes of manhood, Mud is more ambitious than its taciturn style might at first suggest, and Sheridan is such a natural, so centered, that even — especially — in moments of great vulnerability he commands the screen.

To Nichols, authenticity obviously means a lot. Not since Billy Bob Thornton’s first forays into screenwriting has a native Arkansan managed so keenly to exude the Right Hollywood Stuff without forgetting where he comes from. It helps to understand how a sense of place becomes a sense of people. And it helps to build your movie around someone like Tye Sheridan, in whom that understanding seems innate.