As a volunteer teacher in the Samoan islands, author Stan Carter could see a line of volcanoes through his classroom windows. Inspired by Robert Louis Stevenson's Treasure Island as a child, he finds himself drawn to the volcanic mountain known as Matafao, despite the warnings of his students that no one ever goes up there. He sees the volcano daily from his school, and before long his desire to climb Matafao in search of openings into its interior becomes an obsession. When three of his students beg to accompany him, he decides that it is time to act on his desire to climb the volcano. But as they trek up one of its arms in an attempt to explore a volcanic vent, the trip goes awry when one of the boys mudslides into the neck of the volcano. The four of them then battle a jungle of caves and waterfalls, facing numerous dangers and obstacles in their struggle to escape Matafao.