The Adventures of Huckleberry Finn is a novel by Mark Twain about Huck, a mischievous boy, who runs away from his drunken father. Huck meets up with Jim, a runaway slave and they travel down the Mississippi on a raft. The two escape through various misadventures, including the family feud between the Grangerfofrds and Shepherdsons and the conning "duke and king." Finally, Jim is captured on the Phelps' farm, Huck plans an escape and, finally, it is revealed that Jim is now a freeman and Huck's father has died.
Huck begins the novel by recounting the events at the end of The Adventures of Tom Sawyer , in which he and Tom discovered $16,000 in gold. He is now living with the widow and her sister, Miss Watson, and they are doing their best to civilize him. His father soon returns to town and begins causing trouble, trying to get his hands on Huck's money and blocking efforts by Judge Thatcher and the widow to become Huck's legal guardians. He kidnaps his son and keeps him under strict supervision in a cabin in the woods. He locks Huck up when he is not there to watch him. One day while he is in town, Huck saws his way out of the cabin and creates a scene which makes it look as if someone has killed Huck and run off with all of their supplies. He takes the supplies in a canoe he had found and goes to Jackson's Island, in the middle of the Mississippi River.
On the island he meets his friend, Miss Watson's slave, Jim. Jim explains that Miss Watson made a plan to sell Jim to a slave trader in New Orleans, which would take him from his wife and children. He ran away to avoid it and has been hiding on the island since the night of Huck's "death." Huck is surprised but swears to keep the secret. They live on the island while they can, but Huck sneaks over to town and finds out that a party of men are planning to search the island. They pack up their raft and leave.
They float down the river and experience days of tranquility. They move down the river at night and hide during the day. One night they come across a wrecked steamboat and investigate. They come across a gang of robbers and while they are occupied, their raft breaks free and floats away. They steal the robbers' boat and recover their raft. Huck tries to save the robbers by notifying a ferryboat watchman of the presence of people on the wreck.
Huck and Jim plan to go to Cairo, Illinois, where they can sell their raft and then take a steamboat up the Ohio River to the free states. When they are close, they get trapped in a fog and separated. They call out to one another in order to stay together but they soon lose each other. Huck goes to sleep and when he wakes up he sees the raft and is able to catch up to it. He plays a trick on Jim, pretending that the fog never happened that Jim had dreamt their separation. Jim eventually finds out it is a trick and scolds Huck for being insensitive. Huck is ashamed and he apologizes to Jim.
As they get closer to Cairo, Jim begins to talk more about his plans for the time after he is free. This leads Huck to think about the repercussions of helping Jim escape. He starts to doubt his decision. He gets close to telling two men he meets but is unable to and decides that he will stay true to his promise to Jim.
They continue on and realize that they passed Cairo the night of the fog. They decide that they should take their canoe up the river but the canoe disappears. Their only option is to continue down the river until they have the chance to buy a new canoe. As they make their way their raft is run over by a steamboat and they are separated.
Huck finds himself outside a log cabin and he is taken in by the Grangerford family. They are a genteel Southern family who are part of a longstanding feud with the Shepherdson family. While Huck is there, Sophia Grangerford runs off with Harney Shepherdson and most of the family is killed in the resulting fighting. Huck finds Jim and they escape.
They soon meet two con-artists who claim to be a king and a duke. They take over the raft and Huck becomes a part of their cons. They make a decent amount of money performing a "low-comedy" called "The Royal Nonesuch." Then they impersonate two Englishmen who are the brothers of a deceased man, in order to steal the inheritance. Huck watches as they try and take everything from a group of orphan girls. He eventually develops a plan to expose the king and the duke and give the money back to the girls.
He does not rid himself of the duke and the king. Next they land near a village called Pikesville. While Huck is distracted, the king sells Jim to Silas Phelps. They leave Huck behind and he has to decide if he will try to help Jim escape. He debates both sides and after considering all that Jim has done he decides once and for all that he is going to help him get his freedom.
He goes to the Phelpses' farm and soon realizes that they think he is Tom Sawyer. Comfortable in his new situation, he intercepts Tom before he reaches the farm and enlists his help. Tom is very keen to help Huck free Jim and they develop a plan to do it. Tom insists on following the rules established by all the adventure novels that he has read while Huck wants to do things simply. He follows Tom's lead, helping him carry out his crazy schemes. Their plan is to dig Jim out. Jim is forced to participate, doing things like keeping a journal on a shirt and making inscriptions on the wall. They send him objects that he needs by placing them in his food and bake a ladder made out of sheets into a pie for him. Their surreptitious thefts of random objects from the house makes Aunt Sally frustrated and angry.
When they think that Uncle Silas might be ready to advertise Jim in the newspapers, Tom sends out anonymous letters which warn the family that a gang is trying to steal Jim. The family becomes upset and anxious and a group of people come to help. They manage to get Jim out and to the island where Huck hid the raft but in the process, Tom is shot in the leg. Huck goes to get a doctor and Jim agrees to stay with Tom, though it means sacrificing his freedom.
After a couple of days Tom is returned home by the doctor and Jim is placed back in his shanty with extra precautionary measures. Once Tom regains consciousness he tells Aunt Sally everything and explains that it was all his idea. He informs them that Miss Watson died and gave Jim his freedom in her will, since she always regretted trying to sell him. Jim is immediately released and Tom gives him $40 for his troubles. Huck decides that he will head for the Territory, in order to avoid Aunt Sally's civilizing influence.