Writer-director Jeff Nichols charts the rude awakenings that intrude upon youthful idealism. His coming-of age story is seen from the perspective of Ellis (Tye Sheridan), a 14-year-old on the cusp of hitting his growth spurt.

While exploring a small island on the Mississippi River, Ellis and his best friend Neckbone (Jacob Lofland), discover a boat wedged 15 feet up a tree. The pair has just begun fantasizing about using the boat for their new clubhouse when they spy unusual footprints. Those boots, with a cross emblazoned on the heel pads, belong to Mud (Matthew McConaughey), a mysterious man who arrives to claim the boat as his own.

Because the mystery man, who is clearly in some sort of trouble, treats the boys as equals, they are persuaded them to bring him food and supplies. Ellis, who’s home life has recently taken a turn for the worse, is captivated by Mud’s lifelong love for a woman named Juniper (Reese Witherspoon). Mud’s attachment, and his protective instincts, are responsible for his current troubles.

Back home, Ellis’s parents argue in hushed, intense tones. From their Mississippi River houseboat, Ellis’s father Senior (Ray McKinnon), makes a meager living catfishing, while his mother Mary Lee (Sarah Paulson), wants to leave their cramped, dilapidated quarters for a nice apartment in town. “I’m no townie,” Ellis tells Neckbone, who resides with his womanizing uncle Galen (Michael Shannon), down river in a trailer.

Enigmatic Tom Blankenship (Sam Shepard) stares across the river at Ellis from a larger, slightly nicer, houseboat. Having never spoken to the man, Ellis is intrigued to learn that Blankenship and Mud share a long history.

Ellis and Neckbone, largely overlooked by their caretakers, scavenge boat parts for Mud and ferry messages to Juniper, who is encamped at a local motel. Matters become complicated when King (Joe DonBaker), the powerful father of the man Mud wronged, arrives in town with his gang of thugs.

The boys’ secret lives and Ellis’ attraction to pretty girls are easily recognizable signs of early adolescence, but the film’s seemingly lazy cadence holds many surprises. Nichols carefully constructs his characters to remain true their values, yet exceed our expectations. They most often surprise us in satisfying ways, within a story that maintains an equitable mix of action and motivation.

Insisting that his cast members read or reread Huckleberry Finn, elements from Nichols’s inspiration work their magic on his story. Some may call it old-fashioned, but I believe he’s produced a modern American classic.