What happens to Jack when Ralph mentions rescue in Lord of the Flies?
In William Golding's novel, Ralph and Jack serve as foils of one another. Ralph is associated with society, its rules, and its restrictions; his main goal is to get the boys rescued and adopt certain moral or adult behaviors until they are. Jack, on the other hand, takes the marooning as an opportunity to reject society and embrace instinct, which Golding paints as horribly bestial.
Over the course of the novel, Ralph and Jack interact several times regarding the theme of rescue. I can't be sure which of these specifically you are referring to, but generally, Jack feels unjustly chastised by Ralph, and responds through some combination of withdrawal and then aggressive defensiveness. He also usually attempts to change the topic of conversation to one in which he excels, rather than Ralph.