In the fifth book of this award-winning national park series, Tommy "Bubba Jones" and his sister, Jenny "Hug-A-Bug," uncover amazing facts about Yellowstone National Park while on a mission to solve a park mystery. This is no ordinary brother and sister duo; they are part of a legendary time travel family with a mission to preserve and protect our national parks and they have developed a reputation for solving mysteries. As they time travel back hundreds, thousands, and millions of years, they not only learn about the past but also experience it. They encounter wild creatures and ancient plants. They meet members of the early park expeditions and encounter the U.S. Army who once served as the park stewards. They learn about the Native Americans that call this land home. They learn all about the volcanic activity and unravel some of the park's secrets. Discover Yellowstone National Park in a whole new way.