Ironcially, it is Simon who, early in the novel, expresses the least fear. He understands that fear is a dangerous and useless emotion, and insists on going in search of the beast in order to prove that there is nothing to fear. However, what Simon finds ignites the fear in him. He realizes that the beast is the dark side of boys' nature. He fears what the boys will do to each other as they become less civilized, and foresees that what has happened to the boar will happen to the boys.
Simon is the least fearful of all the boys on the island. One can see this when Simon addresses the issue of a "beast" on the island. It is Simon that warns the boys of the internal threat that looms about the island. But it is in his subconscious state in the presence of the Lord of the Flies that he realizes the terrible fate of the boys on the island. This event causes him to become fearful.