While lost in a tunnel at Carlsbad Cavern, thirteen-year-old Jack, eleven-year-old Ashley, and their eight-year-old foster brother, Sam, think bats and darkness are their worst problems, until they stumble across thieves.
Visiting Zion National Park with his family, twelve-year-old Jack encounters two mysteries, the strange behavior of a band of wild mustangs and the possibly sinister actions of his new foster brother, a Shoshone boy.
While visiting the Everglades National Park with their parents, the Landon children uncover the mystery of dying manatees and learn important lessons about the natural environment.
The Landon family travels to Glacier National Park to investigate why grizzly bear cubs are disappearing and becomes involved with a ten-year-old Mexican runaway boy.
While she studies condors in the Grand Canyon a scientist's life is threatened, and the strange, hostile, teenage computer whiz in her family's foster care might be involved.
Visiting Zion National Park with his family, twelve-year-old Jack encounters two mysteries, the strange behavior of a band of wild mustangs and the possibly sinister actions of his new foster brother, a Shoshone boy.
Jack, Ashley, and their parents visit Hawaii where they meet a Vietnamese boy who is going to live with his American grandfather whom he has never met, and are pursued by the Goddess Pele.
Twelve-year-old Jack and his younger sister visit Mesa Verde National Park, where they delve into the park's history while gradually uncovering the mysterious past of their family's teenage foster child Lucky.
