Search for the Serpent's Stone. The Geocaching Mystery Series, #4

The Australian Outback holds more than just heat-it hides secrets. Allie Ashe and her friends Drake Decker, Ingrid Snyder, and Geneva Benson are thrilled when Allie is invited to the first ever Australian Outback Geocaching Invitational. Select teams from around the world gather to compete in this high-stakes event, with a large cash prize, and more intriguing, a historical artifact to be won. Once the contest begins, the coordinates lead them to locations off the beaten path, and it doesn't take long to discover how high stakes the competition really is.
As the group discovers ancient unknown symbols, they rely on their new Aboriginal friends for guidance. The more they explore the Australian Outback the more they realize the competition isn't just about winning-it's about something else. As they try to respect the land and the Aboriginal culture, they're pitted against teams that aren't what they claim to be. They also need to contend with a harsh environment that threatens them at every stop as they follow clues to find what they're searching for: the legendary stone of the Rainbow Serpent.
  Search for the Serpent's Stone is the fourth book in the Geocaching Mystery Series, where the four friends compete in what may be their most dangerous geocaching event yet.