| Director | Jeff Nichols |
|---|---|
| Genre | coming-of-age film, drama film |
| Runtime | 131 min |
| Country | United States |
| Budget | $10 million |
| Box office | $32.6 million |
Ellis and Neckbone, two teenage boys living near DeWitt, Arkansas, are excited to find an abandoned boat lodged in a tree on a small island in the Mississippi River, a remnant of a past flood. However, the boat is already inhabited by a man named Mud, a disheveled but charismatic fugitive whom the boys encounter a short time later. Mud asks for some food, promising them the boat in exchange once he is gone.
Returning with food, the boys ask Mud why he is hiding out. Mud reveals he is waiting for his girlfriend Juniper, whom he describes as beautiful, with distinctive nightingale tattoos on her hands. The boys later spot Juniper in town. Meanwhile, Ellis falls for an older girl named May Pearl.
Ellis learns that his parents are heading for divorce over his mother's desire to move into town. This threatens their old river houseboat: if no longer used as a residence by the owner, it will be demolished by the River Authority. Later, at a roadblock, Ellis finds out Mud is a wanted fugitive, but denies having seen him.
The boys confront Mud over the discovery. Mud explains that he killed a man who had gotten Juniper pregnant and pushed her down a flight of stairs, causing her to lose the child. Mud now plans to use the boat to escape and promises the boys his pistol instead for their continued assistance.
Mud sends Ellis to his neighbor Tom Blankenship, an older father figure from Mud's childhood, to ask for help. Tom agrees to talk to Mud; however, upon learning Mud is in trouble over Juniper again, he refuses to help. Mud gives the boys a note for Juniper. They find her motel room where Carver—the brother of the man Mud killed—is abusing her. Ellis and Neckbone tell Mud about the man, and Mud realizes that the family of the man he killed has come for revenge.
Stealing machine parts and an outboard motor from junkyards, the boys help Mud repair the boat, and coordinate a plan with Juniper to bring her to Mud so they can escape together down the river. On the designated day, Juniper does not show up. Ellis and Neck find her flirting with another man at a nearby bar and tell Mud what has happened.
Ellis brings a note from Mud to Juniper, telling her he accepts that it's over between them. Juniper tells Ellis that she loves Mud, but that he is a born liar and she cannot spend the rest of her life following his itinerant lifestyle. Ellis is deeply disillusioned by the sudden dissolution of what he believed to be a couple deeply in love. Soon after, May Pearl rejects and humiliates Ellis in front of her friends. These events seem to confirm for Ellis his father's admonishment, in the wake of the pending divorce, that women cannot be trusted.
Ellis confronts Mud and calls him a liar and a coward for giving up on Juniper. Running away, Ellis falls into a pit containing cottonmouths and is bitten. Mud jumps in and rescues him, racing to get the unconscious Ellis to a clinic on the mainland. Recognizing Mud, one of the hospital employees calls the police, who tip off Carver and his father King.
Evading his pursuers, Mud gets back to the island where he and Neckbone launch the repaired boat into the water. As promised, Mud gives Neckbone his empty pistol. Mud wants to say goodbye to Ellis, so Neckbone takes him to Ellis's family's houseboat, where he is recovering. Mud sneaks into Ellis's room, and Ellis tells Mud he is sorry for what he said. Mud replies Ellis was right about most of what he said, and that he is not a good man. Ellis then shares his father's advice about women. Mud disagrees, and says that Ellis is a good man and if he finds a girl half as good as he is, he'll be alright.
While Mud is in Ellis's room, Carver and his posse arrive and start shooting. Tom, a former Marine marksman, fires from his boat using his old sniper rifle, killing several attackers from across the river. Mud saves Ellis and tries to get away but is shot as he dives into the river. The police arrive and find all the posse members dead. One trooper calls King to tell him that his other son is now dead. Police divers search for Mud's body all night. The morning after the shootout, Tom disappears.
Ellis's parents separate. He and his mother move to an apartment in town and Ellis's father gets a new job far away. Ellis and Neckbone watch the houseboat get demolished as Ellis shares that he is uncertain of Mud's fate but still believes he was protecting Juniper. As Ellis's father departs, he tells Ellis to take care of his mother because this change is hard on her too, showing a more mature and changed attitude toward their situation. He assures Ellis he'll see him again in a week and tells Ellis he loves him, to which Ellis reciprocates. Ellis sees some attractive older teenage girls in his new neighborhood – one of them waves to him and he smiles.
Several days later, Mud is revealed to be alive and recovering on the repaired boat, driven by Tom. They look ahead at the mouth of the Mississippi River, and south of that, the Gulf of Mexico.