In this adventure, the Landons trail a wounded wolf in Yellowstone National Park. The park is abuzz with rumors of a wolf attack. Meanwhile, a killer stalks the woods. Unaware of the danger, Jack and Ashley are more concerned about rebellious teenage foster child, Troy Haverson. From the opening moments at Old Faithful through 48 action-packed hours, the tension builds - What is lodged in the wolf's radio collar? And what is the meaning of the Native American story of Sin-a-Wavi? A heady mix of suspense, adventure, and moments of tenderness lure readers into this story of kids discovering the natural world. The book's afterword, by Yellowstone's Michael K. Phillips, explores the park's Wolf Restoration Program.