A phantom horse, a missing friend, a dangerous valley filled with abandoned mine shafts...Not exactly what Meg, Becky and Alison were expecting on vacation at the Mustang Mountain Ranch in the Rocky Mountains.Becky was hoping for a peaceful time without her annoying cousin Alison. Alison was supposed to be travelling to Paris with her father. And Meg was planning to meet Thomas. Soon the girls have to organize a rescue party. But will they be in time?