Tom, Huck, and Joe fill their days with all the fun they can imagine: hunting for turtle eggs to cook for breakfast, swimming, running around naked. By Friday they're homesick.
Though they've run away from home and imagine themselves to be independent men, the boys' yearning for home shows them to be still immature. They are learning the hard way that adult independence is less fun than its depiction in books for boys.
Tom wants to stay on the island because he has a secret he can't yet share. When Joe insists on leaving, Tom taunts him about missing his mother, but Joe sets off, and Huck follows him. Abandoned, Tom decides to share his secret. The secret does indeed convince them to stay.
Tom insists on being boss amongst the three, bullying Joe rather than sympathizing with his homesickness. Tom's tendency to boss around his peers establishes him as the authority amongst the boys. As their society mirrors adult society, Tom's tricks of withholding information to manipulate others suggest that for all the reasons he gets punished as a boy, he will one day be a leader among men.
After dinner, Tom suggests he and Joe learn to smoke from Huck, who proceeds to make pipes from some corncobs. Tom and Joe take to tobacco quickly, and begin bragging about how their schoolmates will be jealous. It is not long before both feel sick, and disappear into the woods to relieve themselves. At dinner, both Tom and Joe decline to smoke more.
The boys want to smoke to prove their manhood. Yet they get so caught up in imagining how they'll show off that they fail to restrain themselves and learn the hard way that overindulgence in forbidden substances leads to embarrassing, disgusting loss of control. Once again, the conditions of adult behavior prove less forgiving than those of boyhood.
Joe wakes at midnight, feeling something weird is in the air, and tells the others. A terrible storm breaks out. Their camp is ruined and the sycamore that had sheltered theirs bed is split in two by lightning. They make breakfast, recounting their bravery the night before. Homesick feelings stirring in them again.
A great storm is an event that pirates would often brave. Faced with a real one, the three boys prove to be scared and ill-prepared. At its end they are drenched and lucky to have escaped unharmed.
Tom distracts them from their sadness by declaring that they'll be Indians now, hunting Englishmen. The Indians share a peace pipe. Though Tom and Joe are nervous to smoke again, they are fine.
Tom and Joe have learned to smoke in moderation, and now manage to enjoy this activity as adults might. In the end, it is not so bad acting like an adult, but it is definitely substantially different and less grand than they had imagined it to be.