Mammoth Cave, Kentucky's National Park since 1941, is the scene of this mystery adventure involving Drew, the son of a camp ranger, and Jenny, the daughter of a private cave owner. Jenny's father is bitterly opposed to the National Park as he earns his living exhibiting his cave to tourists. Her brother, furious at the government cave managers, has defaced some of the public property; and Jenny is strictly forbidden to venture within its boundaries. But the essential justice of the caves belonging to the government impresses itself upon Jenny. Together, she and Drew explore the dangerous and fascinating expanses of the underground world, and finally Jenny's family is reconciled with the National Park and join its staff. Vivid descriptions, convincing depiction of character, and breathtaking action combine to make this introduction to another one of America's National Parks as entertaining as it is informative.