Prior to the start of the plot, the novel opens with a series of songs from the notebook of historical American composer Daniel Decatur Emmett. The songs rely heavily on stereotypical representations of Black people, and would have been performed by white minstrel troupes in blackface for the entertainment of white audiences. With this setting and mood established, the novel begins in Hannibal, Missouri, with the enslaved Jim waiting outside the kitchen door of his enslaver, Miss Watson. Two children, Huckleberry Finn and Tom Sawyer, hide in the tall grass and attempt to pull a prank on him, though Huck is hesitant. Huck later confides in Jim and declares that he is his friend. Jim cares for Huck in turn and wants to protect him, especially after learning that Huck’s abusive father has returned. Jim’s world falls apart when Sadie, his wife, overhears Miss Watson’s plan to sell Jim. Fearing that this sale would permanently separate him from Sadie and his daughter, Lizzie, Jim flees across the river to Jackson Island. The next morning, Jim hears a voice and realizes that it belongs to Huck. Huck explains that he faked his own death in order to escape his father. Together, they hide on the island until Huck’s attempt to check on Sadie and Lizzie arouses suspicion. This threat ultimately drives them to sail away, and they almost immediately encounter danger while investigating a wrecked steamboat. A band of robbers is on board, and Jim and Huck must quickly flee after stealing their boat with treasures, books, and clothes inside. 

As they continue their journey, Huck becomes increasingly more curious about Jim and the institution of slavery. He questions the practices and beliefs that white society upholds while Jim vows to challenge them by making money and buying Sadie and Lizzie their freedom. Unfortunately, Jim and Huck become separated when a steamboat strikes their raft. Jim eventually wakes surrounded by four Black men who reveal that he has arrived in Illinois. They offer their assistance, and Jim asks for help acquiring a pencil. He hides while waiting for one of the men, Young George, to bring him a pencil, reading each of the books that he found in the robbers’ boat. Jim enjoys writing once he has a pencil, but seeing a white man whip Young George for having stolen it horrifies him and forces him to run. 

Coincidentally, Jim runs into Huck, and they quickly return to the river. Their progress stalls, however, when Huck ventures out alone and returns with two white men. Running from barking dogs, the men reveal that they are wanted for various crimes. Huck admires their grandiose claims of noble lineage, but Jim quickly recognizes that the self-proclaimed Duke and King are frauds. The Duke and the King take advantage of Jim’s precarious position, forcing both him and Huck to participate in criminal schemes. Jim and Huck attempt to run, but the Duke and the King eventually catch them and propose an even crueler plan that involves repeatedly selling Jim. One night, the Duke and the King take Jim to a livery and ask Easter, an elderly Black man, to shackle him. Easter removes the chains once Jim’s captors have gone, an act which leads the Duke and the King to beat him in the morning. Easter’s owner, Mr. Wiley, declares that he will keep Jim while Easter heals. This event ultimately frees Jim from the Duke and the King, but they manage to take Huck.

Easter begins teaching Jim how to make horseshoes, and when Wiley returns, he demands that they sing for him. This sound brings a group of white men to the doorway, and their leader announces himself as Daniel Decatur Emmett of the Virginia Minstrels. Emmett offers to buy Jim as he is in search of a new tenor for their group. Wiley agrees, and Jim follows the group away. He is baffled by the decent treatment he receives. A large man named Norman helps Jim put blackface make up on, and as he does so, he reveals that he is actually a Black man passing as white. Jim feels uncomfortable as he marches with the minstrel troupe, and he becomes even more uneasy when a white man approaches and touches his hair, believing it to be a wig. The man returns to the group’s camp that night to touch Jim’s hair again, suggesting he harbors suspicions about the group’s claim that Jim is white like the rest of them, which forces the group to move to a new town.

Knowing the risk that Jim faces, Emmett leaves him behind at the camp while the rest of the group performs. Jim runs, stealing Emmett’s songbook in the process. Norman also escapes and meets Jim in the woods. Together, they come up with a plan to earn money to buy Sadie and Lizzie. Norman pretends to be a white man selling Jim, and he eventually finds a buyer in a man called Henderson at the sawmill. Henderson is a brutal master, lashing Jim and raping a girl named Sammy. Jim sees his daughter in Sammy, so they escape together. Although they cannot initially find Norman at their meeting spot, they eventually reunite and decide to put an end to their plan of selling Jim. Jim, Norman, and Sammy keep moving, but Henderson manages to track them down. They flee, and when they finally reach safety, Jim and Norman discover that Sammy, hit by one of Henderson’s bullets in the chaos, is dead. They bury her on the shore before heading north.

They sneak onto a passing riverboat, although they almost drown in the process. Brock, a slave working in the ship’s boiler room, suspects that something is going on between Jim and Norman and continually threatens to expose them. Any danger that Brock poses, however, is nothing in comparison to the explosion that occurs on board following his manic shoveling of coal into the furnace. The boat sinks, throwing passengers and debris into the river. Jim sees Norman ahead of him, but all of a sudden, he hears Huck’s voice in the opposite direction. Only able to save one, Jim rescues Huck and pulls him safely to shore. Jim reveals that he is Huck’s real father, a fact which Huck initially struggles to understand. He desperately wants to stay by Jim’s side, but knowing that he must keep running, Jim instructs Huck to return to Miss Watson and Judge Thatcher. Many refusals later, Jim finally accepts Huck’s presence, and they make their way back to Hannibal.

Once they arrive, Jim sneaks into his old house only to discover that Sadie and Lizzie are no longer there. He begs Huck to return to Miss Watson to inquire about their whereabouts and spends the night with Cotton and Katie, an enslaved couple who now occupy Jim’s house. The next morning, Hopkins, the overseer, comes in and rapes Katie. Jim knows that he cannot risk staying in the cabin, so he heads out to Jackson Island and waits for Huck there. Jim hides in the brush as white men come and go from the island’s beaches, but his anger drives him to kill Hopkins when he is left behind by his group, drunk and alone. Having received few details from Huck about the new location of his family, Jim sneaks into Judge Thatcher’s library to search for a bill of sale. Judge Thatcher discovers him, and with Hopkins’s gun, Jim forces him to show him how to get to the Graham farm on a map. He then kidnaps Judge Thatcher and makes him row him along the river before tying him to a tree. Jim runs for three more days before he makes it to the farm. Using a match from Judge Thatcher’s, Jim sets fire to the cornfield, an event that allows all of the slaves to flee into the woods. He shoots the farm owner with Hopkins’s pistol before fleeing into the night alongside Sadie and Lizzie. Jim, Sadie, Lizzie, and two other escaped slaves eventually make their way to Iowa, and Jim embraces his true identity as James.