Gene is a prisoner of his own guilt and fear. He feels tremendous guilt for the injury he has caused Finny, and he lives in fear that the other boys will discover the truth of what happened in the tree. When Brinker corners Gene in the Butt Room and starts nibbling around the edges of the truth, Gene responds first in anger, then by making up a ridiculous story to explain what he had done to Finny:
Well . . . first I stole all his money. Then I found that he cheated on his entrance tests to Devon and I blackmailed his parents about that, then I made love to his sister in Mr. Ludsbury's study . . . .
Through this silliness, Gene manages to defuse Brinker's "inquiry," making him look foolish in the process.
Prior to the confrontation in the Butt Room, however, Gene made two serious attempts to free himself from his guilt. He tried twice to confess the truth to Finny, once in the infirmary at Devon shortly after Finny's injury and a second time at Finny's family home in Boston. On both occasions, Gene does not succeed in saying what he needs to say, that he caused Finny's fall. In the infirmary, he is interrupted by Dr. Stanpole and a nurse. In Boston, he cannot complete his confession because Finny can't bear to hear it:
It struck me then that I was injuring him again. It occurred to me that this could be an even deeper injury than what I had done before. I would have to back out of it, I would have to disown it.
Thus, Gene continues to suffer within the prison of his own making. He cannot escape even by enlisting in the military, which he decides to do. Finny's return to school makes it impossible for Gene to leave Finny behind, hurt and helpless.