Ralph is one of the primary characters in William Golding's Lord of the Flies; he is one of the older boys and looks like a leader, so the boys on the island vote for Ralph to be their leader. Ralph struggles in many areas, but there is one thing on which Ralph never wavers: fire.
Jack, one of the other leaders on the island, is consumed (obsessed) with hunting. When he is questioned about it, Jack is quick to say he hunts because the tribe needs meat; however, no one believes him. Ralph's obsession is much less selfish, as he truly is concerned about the welfare of all the boys.
Ralph talks about keeping the signal fire lit almost from the very beginning, but of course his concerns intensify as the novel progresses and they continue to be stranded on the island. In chapter five, Ralph says:
"The fire is the most important thing on the island. How can we ever be rescued except by luck, if we don't keep a fire going? Is a fire too much for us to make? Look at us! How many are we? And yet we can't keep a fire going to make smoke. Don't you understand? Can't you see we ought to--ought to die before we let the fire out?"
At one point a ship passes, but there is no smoke and therefore there is no rescue. Ralph never says it, but he is aware that the only way they are going to escape this island is through a rescue--and he intuitively knows that the rescue must be sooner rather than later.
Keeping the signal fire lit is the thing Ralph is most passionate about in this novel.