Pap begins hanging out around the town and demands Huck give him money every few days. When the widow tells Pap to get away from her property, he kidnaps Huck and takes him three miles upriver to a log cabin. Pap carefully locks the door and never leaves Huck's side without making sure that Huck cannot escape. Huck enjoys being free from school but soon gets upset that he is being beaten so much.
Searching for a way to escape, Huck discovers part of a saw that is missing its handle and starts to saw off a log in the rear corner of the cabin, but is forced to stop when Pap returns. Pap is drunk and makes Huck go outside and bring in all the supplies he has brought from town. Pap proceeds to drunkenly curse everyone he has ever met and spends a significant part of his tirade criticizing the government.
Huck hopes to escape after Pap falls asleep, but Pap has a fitful night, and Huck is afraid he might wake up and catch him trying to get out of the cabin. At one point Pap jumps up thinking he is covered with snakes. Later, he dreams that the angel of death is after him and he starts to chase Huck around the cabin with a knife. Huck runs for his life and manages to survive after Pap falls asleep again. Huck then takes down the gun and holds it for protection.
Pap and Huck go out into the woods to hunt for game. While there, Huck sees an abandoned canoe on the river and jumps in to get it. When he realizes that Pap did not see him snare the canoe, he hides it in a little stream for future use and returns to Pap. Next, Huck fetches a wooden raft from the river with timber that is worth about ten dollars. Pap locks Huck into the cabin and takes the raft to town in order to sell it.
Taking advantage of Pap's absence, Huck quickly finishes his sawing and climbs out of the cabin, taking everything worth any money to his canoe. He axes down the front door and goes hunting for game. Huck shoots a wild pig, butchers it inside the cabin, and spreads the blood on his shirt and the floor. He also carefully lays some of his hairs on the now bloody ax to make it appear as if he has been killed. Huck cuts open a sack of flour and marks a trail indicating that the killer left via a lake that does not connect to the river. Thus, he prevents anyone from searching along the river for anything more than his dead body.
As Huck is finishing, a man appears nearby in a skiff. Huck recognizes that it is Pap returning early and that he is sober. Immediately, Huck jumps into the canoe and pushes off. He floats downstream until he reaches Jackson's Island, a deserted stretch of land in the middle of the river. Huck ties up the canoe and satisfied with his work, settles down to get some sleep.
Huck wakes up on Jackson's Island late the next day and hears a cannon being fired. A ferryboat filled with his friends comes down the river firing a cannon in hopes of bringing his dead body to the surface. The search parties have also set loaves of bread filled with mercury afloat, believing the mercury and bread will be attracted to his body. Knowing the loaves will be floating around the area, Huck searches for one and enjoys eating it for lunch.
After a few days, Huck begins exploring the island. While following and hunting a large snake, he accidentally stumbles into a clearing with a still smoking campfire. Out of fear, he retreats to his campsite and paddles over to the Illinois side of the river. However, he soon returns for the night and sleeps poorly as he is overwhelmed with fear for who else might be inhabiting the island.
The next morning Huck decides to find out who else is on the island with him. He paddles his canoe down to the other campsite and hides in the brush. Soon he sees Jim, the slave Tom Sawyer played tricks on. Out of joy for finding a friend on the island, Huck rushes out and greets him. Jim nearly dies of fright when he sees Huck, whom he believes to be dead. Huck tells him the story about how he faked his murder. Jim relates that he overhead Miss Watson telling the widow that she was going to sell him down the river for a good sum of money. To avoid being sold, Jim ran away, and has been hiding out on Jackson's island.
Jim starts to tell Huck about various superstitious signs which the slaves watch out for. When some birds go hopping along the ground, stopping every few feet, Jim comments that means it will rain soon. He also tells Huck a story about how he lost a large sum of money, fourteen dollars at the time, by speculating. First, Jim bought a cow that died, and then invested with another slave who was setting up a "bank." Unfortunately, the bank lost all its money and poor Jim had nothing left.
Jim and Huck explore the island together and discover a cavern atop a hill in the middle of the island. They paddle their canoe to the base of the hill and then haul their equipment into the cave in order to keep it dry. The storm Jim predicted arrives that night, and the river rises for more than twelve days straight.
Huck and Jim go out on the river at night to pick up drifting logs and other objects that happen to float downstream. One night, they capture a large raft which they will later use to navigate the river after they leave the island. Later on, they see a whole house floating downstream and climb into it to salvage some of the goods. Jim finds Huck's Pap lying dead on the floor of the house, but refuses to let Huck see the man's face and does not reveal that it is Pap. Jim sees Pap was shot in the back while obviously attempting to rob the house.
Huck is thrilled with all the things they managed to get from the house and tells Jim that he wishes they could have fun like that more often. Huck is also still curious about the man in the house but Jim refuses to talk about him. Huck mentions that he thought they would have bad luck after he brought a snakeskin into the cave, not great luck like what they were having. Always superstitious, Jim warns Huck that the bad luck is still coming.
Three days later, Huck tries to play a trick on Jim by leaving a curled up dead rattlesnake under Jim's blanket. But when Jim crawls into the bed he gets bitten in the ankle by the snake's mate. Huck kills the mate and sheepishly carries both snakes far away from the cave, embarrassed by the results of his behavior. Jim takes the jug of Pap's whiskey and drinks himself into a drunken stupor to avoid feeling the pain of his swollen leg. It takes Jim four entire days to recover from the bite and Huck vows to never touch a snakeskin with his hands again.
In order to catch up on what is happening in the town, Huck dresses up as a girl and goes to the village. He stops at a house where he sees a woman knitting. Since she is new to the town, Huck figures he can talk to her without being recognized.
These five chapters reveal a great deal about Huck as a person. Huck emerges as a vibrant character who fights powerfully for his life. Huck's capture and escape from Pap demonstrate his genius for innovation, as does his ability to live alone on Jackson's Island. Huck does not need anyone's help to survive, and the only indication that he is not completely happy is his comment that he sometimes gets lonely.
Huck's personality is quite uniquely established throughout these chapters. He exhibits humility in that he constantly underplays his brilliant ideas. Thus, when he fakes his death, he says that even Tom Sawyer would have been proud of the charade, indicating that Tom would have been able to fake it better but that it was a good enough to earn some praise. The innocent side of Huck is also revealed in his encounter with Jim. Jim swears him to secrecy before revealing that he has run away from Miss Watson. Huck is immediately faced with the responsibility of protecting Jim or telling the town the truth. He chooses to stay with Jim because, as a young boy who has lived outside of main stream society for quite some time, he still lacks the prejudices of the older folks in his town. This youthfulness is reinforced by the image of Huck dressing up as a girl at the end of Chapter 10.
The strength of character that leads Huck to refuse to reveal Jim at this juncture of the novel is tested many times during the course of their travels. In a sense, it is Huck's desperate need to not be alone anymore that overcomes his fear of damnation for not turning in a runaway slave. While Tom Sawyer may be his best friend as a playmate, Huck seeks someone who will care about him as a person rather than as a simple play friend. While it is not at all clear that Jim will be able to assume this role, early indications lean towards the development of this relationship as Jim works to get Huck safely inside the cave and out of the rain.
Jim's motive for keeping Pap's death from Huck is unclear. Jim could simply be trying to protect Huck's feelings, but there is also very likely a selfish motive. Jim has just revealed to Huck that he ran away from the widow. Were he to tell Huck that Pap died, there would be no reason for Huck to remain with Jim on the island. Jim fears that Huck might at some point return to town and tell people where he is hiding. Thus, for Jim, it is a life and death decision whether or not to inform Huck of Pap's death.