In this novel, the littluns experience nightmares involving a beast, which heightens the hysteria regarding the presence of an enigmatic, unforeseen monster on the island. Initially, the littlun with a mulberry-colored birthmark is the first to mention that he saw a "snake-thing," which he later refers to as a "beastie." Ralph quickly intervenes and clarifies that the boy was simply having a nightmare. As the novel progresses, the littluns continue to have nightmares and make claims that the beast lives in the sea and comes onto the island at night. In an attempt to ease the littluns' minds, Ralph builds several huts on the beach that will remind the children of home. The nightmares spread fear among the boys, and the hysteria regarding the identity of the beast increases. The nightmares are symbolically a reflection of mankind's inherent wickedness. Despite being on a dream island, where the weather is beautiful and there is plenty of food, the boys' inherent wickedness corrupts their environment, which is represented by their constant nightmares. As the story progresses, the boys' nightmares become a reality when they mistake the dead paratrooper for the beast and completely lose all hope of establishing a civil society on the uninhabited island.

Good question. Yes, dreams are a motif in the novel. The dream as an ideal is there from the beginning; this island is like a new Eden. After that, then, dreams are how and where the boys see and articulate the things they can't face in waking, which means mainly their fears. Dreams are also prophetic. They indicate when further violence, and, especially, further violent tragedy and decay of civilization will be coming. By the end of the book, it is as if the entire waking world has dissolved and the kids are living a dream (a nightmare), one that the adults must wake them from.