After the overnight trip to the beach, what does Gene decide Finny is trying to do to him? What leads Gene to this conclusion? How does Gene feel when he realizes he is wrong?

After Gene and Finny return from their overnight trip to the beach, Gene concludes that Finny is trying to deliberately sabotage his grades by keeping him too busy and distracted to study. He decides this after he fails his trigonometry test, "the first test (he) had ever flunked". Because Finny had insisted that they take the trip to the beach and blithely overlooked every protest Gene had made that he had to study, Gene had not been able to even look at the subject matter the night before. Finny's endless diversions continue even after Gene fails the test with the insistence that he take part in blitzball and the activities of the Super Suicide Society. Angry and frustrated, Gene thinks about their situation and concludes that Finny is jealous of him, and bitterly competitive - because while Gene is

"more and more certainly becoming the best student in the school; Phineas (is) without question the best athlete, so in that way (they are) even..but while (Finny is) a very poor student (Gene is) a pretty good athlete, and when everything (is) thrown into the scales they (will) in the end tilt definitely toward (Gene)".

In Gene's mind now, Finny is trecherously trying to make him (Gene) do poorly academically so that he (Finny) will be the best overall in school.

Gene finally gets through to Finny when he vehemently protests that he can't attend the latest meeting of the Suicide Society because his grades are being ruined. Finny inexplicably listens this time, regarding Gene "with an interested, surprised expression". He tells Gene not to go, explaining simply that he had thought Gene did not need to study, that things "just came to (him)", and he humbly denigrates his own academic ability in comparison to Gene's great intelligence. At this point, Gene is thoroughly confused, and deeply resentful, in the throes of "new dimensions of isolation". On the one hand, he feels guilty for ever having doubted Finny's motives, and is in awe at Finny's nobility; Gene feels he is "not of the same quality as he". On the other hand, this sense that Finny really is so much better than him infuriates Gene, and he goes to the Suicide Society meeting at his own insistence, feeling confused and deeply resentful (Chapter 4).