Huck has become wealthy from his last adventure with Tom Sawyer and that a Widow and her sister, Miss Watson, have adopted Huck into their home to try to teach him good manners. Instead of obeying his guardians, however, Huck sneaks out of the house at night to join Tom Sawyer's gang and pretend that they are robbers and pirates.
One day Huck discovers that his father has returned to town. Because his father always gets drunk, Huck is worried about his intentions. When Pap confronts Huck and warns him to quit school and stop trying to better himself, Huck goes to school just to annoy his father. Huck's father gets so annoyed that he takes him to a forest out in the middle of nowhere.
Even though Huck likes being away from school, his father's beatings have been too harsh. He fakes his murder and runs away. Huck later runs to an island meets Jim there, Miss Watson's slave.
Huck and Jim soon find out that people are coming to search for them. Jim plans to reach the free states. Huck continues to stay with Jim as they travel, despite his all the widow and Miss Watson taught him.
The only time that Huck and Jim feel that they are free is when they are on the raft. Is was stopped when he met a duke and a king. The Duke and the king made them scam other inhabitants.
The Duke and king betray Huck and Jim and sell Jim back into slavery. When Huck goes to find Jim, he discovers that Jim is being held captive on a farm. The owners think that Huck is their visiting nephew, Tom Sawyer. Tom suggests they concoct an elaborate plan to free Jim. Tom's idea based on several of the prison and adventure novels he has read and the act of freeing Jim becomes a complicated farce with rope ladders, snakes, and mysterious messages.
When the escape finally takes place, a pursuing farmer shoots Tom in the calf. Because Jim will not leave the injured Tom, Jim is again recaptured and taken back to the Phelps farm. At the farm, Tom reveals the entire scheme to Aunt Sally and Uncle Silas. Readers learn that Miss Watson has passed away and freed Jim in her will, and Tom has been aware of Jim's freedom the entire time. At the end of the novel, Jim is finally set free and Huck ponders his next adventure away from civilization.