Chapter 1:
The narrator, Gene, returns to the Devon School in New Hampshire, where he was a student with his friend Phineas 15 years ago, just as World War II began.
The narrative shifts back 15 years, to Gene's days with Phineas. On their first attempt to jump off a huge tree into the river, Phineas, being the daredevil, goes firstand Gene is the only one who follows. Gene is normally a conservative, conformist type person, but around Phineas, he consents to break the rules more often.
Chapter 2:
Finny is an anomaly at Devon; he is a good student and athlete, but also a charming, likeable rule-breaker. The substitute headmaster, Mr. Patch-Withers, gives a tea for their class. Mrs. Patch-Withers notices that Finny has used the school tie as his belt, which is a heavy offense. Finny concocts some nonsense excuse, at which Mr. Patch-Withers is taken by surprise, and does not punish Finny.
Finny and Gene come up with the idea for a "Super Suicide Society of the Summer Session," a group for exciting and dangerous things. Gene goes onto the diving limb with Finny, and loses his balance; Finny stops Gene from falling, and Gene soon realizes that his friend saved his life.
Chapter 3:
Some of Finny and Gene's friends begin to join their new club. Finny makes up a game called "blitzball," sort of a variation on rugby and football; the game is a hit that summer.
Finny casually and easily breaks a school swimming record; Finny also refuses to do it again and have it count. Finny proposes that they go to the beach, which means big trouble if they are caught; Gene decides to go along. That night, Finny admits that he considers Gene his best friend, which touches Gene deeply; but somehow Gene can't say the same thing.
Chapter 4:
Finny mocks Gene's scholarly ambition, and Gene begins to believe that Finny is trying to come out ahead. Finny is the best in the school in athletics; Gene knows that he can be the best in