For most serious cave explorers, penetrating deep into the bowels of the earth is a challenge impossible to resist. The very thought of a dangerous caving expedition sets the heart pounding. Rena and Matthew Carling are two such cavers, who have come to a tiny town in the lake territory of Yucatán. They have only one thought in mind, exploring little known caves, where they hope to find ancient Mayan relics. They are living in a temporary structure of palm leaves, set up between two large trees, and two Mayan servants do their housekeeping...