In St. Petersburg, Missouri, during the 1830s–1840s, Huckleberry Finn has received a considerable sum of money following The Adventures of Tom Sawyer and the Widow Douglas and her sister Miss Watson become his guardians. Despite preferring life as an errant boy, Huck stays so he can be part of Tom Sawyer's gang. Huck’s father, "Pap", an abusive alcoholic, tries to appropriate Huck's fortune. When this fails, Pap imprisons him in a remote cabin.
After a delirium tremens crisis, in which Pap tries to kill Huck, Huck fakes his own murder and settles on Jackson's Island, where he reunites with Miss Watson's slave Jim, who ran away after overhearing she was planning to sell him. Huck and Jim decide to go downriver to Cairo, in the free state of Illinois. After a flood, they find a timber raft and a house floating downstream. Inside the house, Jim finds a man who was shot to death but prevents Huck from seeing.[5] Huck sneaks into town and discovers there is a reward for Jim's capture and he is suspected of killing Huck; they flee on their raft.
Huck and Jim come across a grounded steamboat on which two thieves discuss murdering a third. Finding their raft has drifted away, they flee in the thieves' boat. They find their raft and sink the thieves' boat, then Huck tricks a night watchman into rescuing the thieves. Huck and Jim are separated in a fog. When they reunite, Huck tricks Jim into thinking he dreamed the event. Jim is disappointed in Huck when Huck admits the truth. Huck is surprised by Jim's strong feelings and apologizes.
Jim and Huck on their raft, by E. W. KembleHuck is conflicted about supporting a runaway slave, but when two white men seeking runaways come upon the raft, his lies convince them to leave. Jim and Huck realize they have passed Cairo. With no way to go upriver, they decide to continue downriver. The raft is struck by a passing steamship, again separating them. On the riverbank, Huck meets the Grangerfords, who are engaged in a 30-year feud with the Shepherdsons. After a Grangerford daughter elopes with a Shepherdson boy, all the Grangerford men are killed in a Shepherdson ambush. Huck escapes and is reunited with Jim, who has recovered and repaired the raft.
Jim and Huck are joined by two confidence men claiming to be a King and a Duke, and they rope Huck and Jim into aiding in several scams. In one town, the King and the Duke cheat the townsfolk over two nights with a short, overpriced stage performance. On the third, the grifters collect the admission fee from previous audience members bent on revenge, then flee the town. In the next town, the swindlers impersonate the brothers of the recently-deceased Peter Wilks and attempt to steal his estate. Huck tries to retrieve the money for Wilks's orphaned nieces. Two other men claiming to be Wilks' brothers arrive, causing an uproar. Huck flees but is caught by the King and the Duke. He escapes but finds that they sold Jim to the Phelpses. Huck vows to free Jim, despite believing he will go to hell for it.
The Phelpses mistake Huck for their nephew Tom, who is expected for a visit, and Huck plays along. It turns out their nephew is Tom Sawyer. When Tom arrives, he pretends to be his brother Sid, and develops a theatrical plan to free Jim. Huck attempts to warn the King and the Duke that Jim alerted the local residents to their scam but sees them tarred and feathered and being run out of town on a rail.
Tom is wounded during Jim’s escape. Instead of fleeing, Jim stays to tend to him and is arrested and returned to the Phelpses.[6] Tom's Aunt Polly arrives and reveals Huck’s and Tom’s true identities. She explains that Miss Watson has died, and that she freed Jim in her will. Tom admits he knew but wanted to "rescue" Jim in style.[7] Jim tells Huck that Pap was the dead man in the floating house. Huck declares he will flee to Indian Territory to escape being adopted by the Phelpses.
