When the pharmaceutical giant PharmARAMA sponsors Mammoth Cave National Park, a former seasonal cave guide dreams that the cave is in distress and calls him to come immediately. Walt and Barbara visit Bob and Zona in Cave City, Kentucky, where Bob will take Walt on a tour of the cave to assess the threat from PharmARAMA. Before they can get to the cave, Bob is drafted to replace a missing cave guide Bill. While Walt hitchhikes on Keven's Historic tour, jumps to walk the Lantern tour alone, and hitches up with Bob at the end of his Historic tour, he unknowingly sees clues regarding Bill's disappearance. Bob pulls all the clues together and leads the small crew to find Bill before the rogue research director for PharmARAMA can do away with him.

Once rescued, Bill reveals that he is working undercover for the Army's infectious disease research group and that W.G. Anderson is planning to steal a dangerous, gene-splicing bacterium from under the noses of the Park Service and PharmARAMA. Drugged, dehydrated, and concussed, Bill is in no shape to thwart the theft alone. The team organizes support for Bill's operation in advance of the too-late arrival of Bill's Army unit. Can a group of former guides, nearly retired guides, spouses, and friends catch the PharmARAMA research director red-handed?