In chapter seven of William Golding's Lord of the Flies, Ralph and Jack are on the mountain with most of the older boys while Piggy is back at the shelters with the littluns. The older boys are tracking a pig, with Jack in the lead at first, until Ralph rather pushes Jack aside (because he is displaying some uncertainty and fear) and makes a decision to follow a certain pig-run.
Ralph realizes that it is getting late and he takes charge, sending someone to tell Piggy they will be late and worrying that it will grow too dark for the hunt to continue. All of a sudden there has been a shift in power here on the mountain, the place that has been Jack's domain from the beginning. When Jack mocks Ralph in the same way he has always mocked Piggy, Ralph realizes something new in their relationship, something Piggy has been trying, unsuccessfully, to make Ralph understand.
Now it was Ralph’s turn to ﬂush but he spoke despairingly, out of the new understanding that Piggy had given him.
“Why do you hate me?”
The boys stirred uneasily, as though something indecent had been said. The silence lengthened. Ralph, still hot and hurt, turned away ﬁrst.
In this moment, with that question, Ralph knows that Jack will eventually try to kill Ralph, just as Jack is already trying to eliminate all opposition (most especially Piggy). It is a sobering, "indecent" thought, but it is clear in this passage that Ralph's assumption is right because Jack does not deny it.