Simon wants to tell the other boys that 'the beast' on top of the mountain is not an animal with teeth, claws and wngs but simply the dead body of an airman wearing a parachute.
Simon needs to communicate to the other boys that the "beast" they are afraid of is not a physical entity, but rather a manifestation of the darkness that resides within each of them. He tries to convey the idea that the true evil is the inherent savagery in human nature, and that is what they should be wary of.
He suggests that the boys confront the beast.
In Chapter 3 of "Lord of the Flies," Simon's character is shown to be quiet, introspective, and compassionate. He shows concern for the littluns and tries to alleviate their fears by telling them that they will be rescued. Simon's actions reveal his empathy and sensitivity towards others, setting him apart from the other boys on the island.
In Chapter 9 of "Lord of the Flies," Simon is killed by the other boys during a frenzied dance. It is a tragic moment where the boys mistake him for the beast due to their paranoia and fear.
When Simon goes back into the woods in chapter 8 of Lord of the Flies, he encounters the "Lord of the Flies," which is a severed pig's head mounted on a stake. He has a hallucination where the head seems to be speaking to him, and in his delirious state, he realizes the evil within himself and the other boys.
In Lord of the Flies Chapter 9, Simon discovers that the figure on the mountainside is the dead parachutist. He frees the parachutist's lines from the rocks to allow the body to be taken away by the tide. Simon is the only one who realizes the true identity of the figure and tries to convey this information to the other boys, but tragically, he is misunderstood and killed by the other boys during a frenzied dance.
Simon suggests that they should go up the mountain and face the beast, but the other boys do not agree with him in Chapter 5 of "Lord of the Flies". Simon's suggestion highlights his bravery and willingness to confront their fears, which contrasts with the other boys' reluctance and cowardice.
In Chapter 13 of "Lord of the Flies," Simon is mistaken for the beast and is brutally killed by the other boys during a frenzied tribal dance. The boys, consumed by fear and chaos, descend further into savagery and darkness. This pivotal event marks a turning point in the novel as the boys' civilization completely collapses and they spiral into a state of anarchy and violence.
Simon says "maybe it's only us" in Chapter 5 of "Lord of the Flies," on page 89 (Penguin Books edition). He suggests this idea to the other boys during a discussion about the beast and its existence on the island.
In chapter one of "Lord of the Flies," Simon is portrayed as a quiet and introspective character who often sees things in a different light compared to the other boys. He is viewed as kind and sensitive, with a sense of morality and compassion that sets him apart from the more aggressive and power-hungry boys on the island. Simon likely sees himself as someone who embodies these qualities but may also feel isolated or misunderstood by his peers.
Simon has a conversation with the Lord of the Flies (the pig's head on a stick) in the forest, during which he realizes that the beast is actually the darkness and evil within themselves. However, he doesn't get a chance to tell the other boys before he is killed by them during a frenzied dance.
Basically that "the beast" isn't something they can hunt or kill but an evil force inherit to the boys. It also tells Simon that he won't be able to escape and he will only find the beast among the other boys. Which comes true when the boys later kill Simon.
Simon was mistaken for the beast in "Lord of the Flies". He was killed by the other boys during a frenzied tribal dance on the beach.
The other boys initially dismiss Simon's theory about the beast and his explanation that it might be them, choosing to focus on their own fears and doubts instead. They mock him and belittle his insights, showing their inability to comprehend the deeper truths Simon is trying to convey. Simon's message is lost on the others as they continue to prioritize their immediate, tangible fears over considering a more abstract understanding of the situation.