The fall shatters Finny's leg. No one is allowed to visit him in the infirmary. Though no one suspects Gene did anything wrong, he questions whether he purposely made Finny fall. To make himself feel better, he dresses up one day in Finny's clothes. He feels relief when he looks in the mirror. He says "I was Phineas," and is happy that he'd never have to "stumble through the confusions of [his] own character again." By the morning the feeling is gone.
Gene bounced Finny from the branch because Finny was a threat to his identity. He had defined himself as Finny's rival and equal, and then discovered that he wasn't. But because Gene's sense of himself is entirely wrapped up in Finny, it's only when he dresses as Finny, becomes Finny, that he feels comforted.
That morning, Gene runs into Dr. Stanpole, the school physician. He says Finny is improving, but that he'll never play sports again. Gene starts crying. The doctor tells him to be strong, and says that Finny requested to see Gene in person.
The fact that Finny can't play sports hammers home to Gene the enormity of what he's done. It also symbolizes the loss of youthful perfection.
As he goes to the infirmary, Gene thinks Finny wants to accuse him of causing his fall. In the infirmary, Finny is propped up in bed, in a cast, with a tube inserted in his arm.
Just as Gene's envy blinded him before, now his guilt does. Finny in the infirmary resembles an injured soldier.
Gene asks Finny what he remembers. Finny says he lost his balance and tried to reach Gene but couldn't. Gene is furious and asks whether Finny meant to pull Gene down with him? But Finny says he was just trying not to fall.
Rather than confess, Gene acts cowardly: he checks what Finny remembers, and even accuses Finny of trying to hurt him! Gene's still competing with Finny.
Gene asks what made Finny lose his balance. Finny then says he suspects he didn't lose his balance for no reason, but then apologizes for even implying Gene might have caused his fall.
Finny does suspect Gene, but can't bear to face it. This is a mark of Finny's unique goodness.
Gene realizes that his earlier thoughts about their rivalry were "ludicrous," and realizes that, if he were in Gene's situation, Finny would confess. He starts to confess, but just then Dr. Stanpole enters. The summer session ends without Gene and Finny seeing each other again.
The summer was a time of innocence when the boys didn't have to face enlisting in the war. Finny's athletic daring embodied that innocence. Both end together.
On his return trip to Devon for the fall semester, Gene stops at Finny's house. Finny is propped on pillows, a shadow of the athlete that he was at Devon before his fall.
Gene's jealousy has robbed Finny of his identity as an athlete.
After some small talk, Gene tells Finny that he was responsible for Finny falling from the tree. Finny refuses to believe it. Gene realizes that telling Finny the truth only causes more pain, and backs off. They agree to see each other when Finny returns to Devon at Thanksgiving.
It's no surprise that Finny rejects Gene's confession. Finny cannot comprehend that a friend would harm him because he never would harm a friend.
Finny asks Gene if he's going to start playing by the rules now. Gene says he won't play by the rules, but knows that he's lying.
Finny is trying to preserve their youthful innocence. Gene's lie betrays it.