The novel A Separate Peace by John Knowles is told from the point of view of Gene looking back fifteen years later on his days attending Devon School. He attended this boys private school during World War II. While walking through the campus, he flashes back to a day when his friend Phineas first had the idea that all the boys should jump from an enormous tree on campus into the water below. It was the summer of 1942 in New Hampshire. Gene and Finny, as Phineas was known, were considered Upper Middlers, which seems to be the equivalent of juniors, in high school. Phineas was the total opposite of Gene. He was athletic and brave and outgoing.

     The class above them, the seniors, all knew they were bound to shipped off to war. Therefore, they were forced to take accelerated courses, including first aid, and improve physically in preparation. Gene and Finny's class could still read for pleasure and play tag by the river. That day Finny began to strip down to his underpants in order to make the jump from the tree that he had heard many of the seniors had made. He climbed the tree asking his friends which branch the seniors would jump from, as if they knew. He claimed he was contributing to the war effort before leaping off the limb into the river. Once he did it, he wanted to know who would go next. Against his better judgment, Gene leapt from the branch. Elwin Lepellier, also known as Leper, congratulated him but refused to go next. Chet Douglass and Bobby Zane, who had also stood by watching, didn't seem interested in making the leap either.

     Since no one else would do it, Finny rained praise onto Gene. He told Gene that it was good that Gene had him around to shame him into expanding his horizons. Gene didn't want to admit that Finny had convinced him to do it. They got dressed and walked to dinner. Phineas considered authority a necessary evil and didn't care about getting in trouble if they were late to eat, so he put his foot out to trip Gene then jumped on him when Gene fell onto the grass. This turned into a wrestling match. The other boys urged them to quit it, so they stopped and sped up. Gene wanted to show Finny that he didn't care about authority either, so he hip checked Finny back onto the ground, which made Finny smile. They kept goofing around until they were sure they had missed the start of dinner.

     They walked to the dormitory in the back where the students were living for the summer semester. Gene and Finny returned to their room and read from Tess of the D'Urbervilles. Their illegal radio quietly broadcast the news. Gene changed into his pajamas, which Finny refused to wear, before they went to bed.

     In chapter two they realized that Mr. Prud'homme had noticed their absence from dinner. Finny tried to explain how they had been swimming and lost track of time, but Mr. Prud'homme was upset because Phineas had already missed nine meals in the last two weeks. Finny went on to explain that they had decided to jump from the tree in order to prepare for the war in case they lowered the draft age to seventeen. Gene and Finny would both turn seventeen at the end of the summer. Mr. Prud'homme was won over by Finny's story as teachers often were. Finny was a strange combination of a rule breaker and a do gooder. Due to the war, the faculty had also eased up on the boys who m they realized might be enjoying freedom for only a short while longer. They tolerated them being careless and wild. Finally, Mr. Prud'homme let them off the hook.

     Phineas got dressed and chose to put on a pink shirt. He claimed his mother sent it to him and he had chosen to wear it as an emblem to celebrate American progress in the war. Mr. Patch-Withers came up to Finny after history class to ask him about it, but Phineas got away with it. That afternoon they had to attend a tea at the Headmaster's house for the Upper Middle class. He discussed the war with the teachers and their wives. During their conversation, Mrs. Patch-Withers noticed that Finny had used his school tie as a belt, which he often did with his ties. Finny explained that it went well with his pink shirt and "tied" together the bombing in Central Europe that they had been discussing with their own school. Finny said at least he had used something as a belt; otherwise, his pants may have fallen down right in front of Mrs. Patch-Withers. Mr. Patch-Withers laughed at this comment, and once again Finny got away with breaking the rules. As they left, Gene felt honored to have such a person as his best friend.

     They decided to go jump in the river gain. Finny decided they would jump together to cement their friendship. They would form a Suicide Society of the Summer Session, and to be a member one had to jump out of the tree. They stood on the limb, Gene farther out than Finny. Gene began to lose his balance, so Finny grabbed his arm and steadied him. They made their jump and established the new society. On the way home from dinner, Gene thought about how close he came to falling off that limb. If Finny hadn't grabbed him, he could have broken his back or been killed. Finny may have saved his life.