Simon is the best example of a character who is both "heroic and sick". He suffers from epilepsy, & when in throes of a seizure, he hallucinates the Lord of the Flies speaking to him. Other characters continually refer to him as "strange", & he seems to know when he needs to be alone. Often, after a seizure has passed, he finds himself with a bloody nose. all of this would be a reflection of his sickness. Yet he is heroic as well, in that his sickness allows him to discover the true nature of the beast. He realizes it lives within each person, & that in order to defeat the evil, one must face it head-on. He dies while trying to share this with the other boys, showing his courage in attempting to bring knowledge to the rest.
Ralph has moments of both sanity and insanity. Throughout most of the story, he thinks rationally, although not always successfully. He tries to plan carefully, focusing on rescue and shelter. However, he eventually submits to the bloodlust and savagery of the other boys. When Simon rushes to tell them the truth of the beast, Ralph falls on him in a frenzy with the rest. He will recognize his responsibility later, but the fact remains that he willing participated in the murder of another human being. Returning to sanity afterward does nnot exonerate him from his actions.