Lord of the Flies opens with two boys meeting each other during their search for fellow survivors after their evacuation airplane has, somewhat futuristically, jettisoned its passenger cabin onto an uninhabited tropical island. The boys are Piggy and Ralph. It is quickly established that there are no adults on the island, a fact that Ralph seems to relish in a distinctly boyish way, but that Piggy finds rather alarming. It is Piggy who suggests "calling" the survivors together, using a large conch shell as a horn. He also suggests that the survivors must be organized so that they can better provide food, shelter, and safety while doing everything possible to hasten the group’s rescue. The first order of business is to elect a leader, presumably from among the older boys. Though Piggy clearly has the intellectual qualifications for leadership, his appearance and manner make him an object of the others’ scorn. Instead, it comes down to a choice between a somewhat reluctant Ralph and Jack, who is the apparent leader of a group of choirboys. Ralph wins, a result of his being the bearer of the conch shell, which, having brought them all together, has become a symbol of authority.
Rather than resolving the issue of leadership, this development begins a power struggle between Jack and Ralph. Allegiance to one or the other divides the group as the two boys move in opposite directions. Following Piggy’s lead, Ralph begins to establish the rudiments of civilization. The boys set down rules and responsibilities: no urinating near the source of fresh water, the signal fire must be kept burning, and everyone must help in building shelters. Jack and Roger, another of the older choirboys, soon become more interested in hunting wild pigs, both for the sake of meat and for the sake of the hunt itself. Other boys follow their lead, abandoning their duties. During one such episode, a distant ship sails by as the signal fire lies dormant. Accusations lead to a conflict, and Jack withdraws from the main group along with his followers. The separation is not peaceful. Then Jack’s gang steals Piggy’s glasses—the fire starter—leaving Piggy virtually blind and the rest of Ralph’s group without the hope of fire.
While the younger boys had qualms from the start with regard to various imaginary monsters, fear begins to play a more pivotal role when the corpse of an airman arrives on the island by parachute. Seemingly animated as the parachute fills with wind and then is deflated, the corpse becomes "the beast of the mountain" to the boys. Jack and his followers make a sacrifice to the "beast" following a particularly brutal slaying of a pig. The pig’s head is stuck on a pole, attracting swarms of flies (hence the book’s title). This act signals a renewed reign of terror. Simon, a sensitive, insightful boy who has remained loyal to Ralph, looks beyond the airman’s bizarre appearance and discovers the truth—or, rather, several truths—about the "beast." First, the object fastened upon is nothing but a dead man. Second, the object the boys fear is inside them and cannot be hunted with spears or placated with sacrifices. When Simon tries to tell Jack and his hunters what he has found, he is mistaken for the "beast" and killed outright, a casualty of the ritualistic frenzy of the hunt.
Piggy is next to fall victim to what has now become a veritable orgy of violence. (The conch shell is destroyed at almost the same moment as Piggy is killed.) Particularly vicious in all this is Roger, who has become discernibly sadistic during his time on the island. Having learned Ralph’s whereabouts from one of the younger boys fearful for his life, Roger and Jack start a brushfire to flush their prey out into the open. Their massive manhunt is about to come to a successful conclusion when, rather ironically, a rescue team arrives, drawn by the flames that are engulfing the island.