Mysteries in our national parks

Twelve-year-old Jack, his younger sister, and the family's teenage foster child Troy go to Yellowstone National Park, where Jack's mother, a wildlife veterinarian, is investigating the report that wolves reintroduced to the park have killed a dog there.

While their parents study why wolverines are disappearing from Alaska's Denali National Park, Jack and Ashley are stranded in a remote area with their mysterious new foster brother when a hit man's bullet triggers an avalanche.

While their mother investigates a series of bear attacks in and near Gatlinburg, Tennessee, Jack and Ashley learn about country music and Cherokee people from two new friends, one of whom is keeping a secret.

Twelve-year-old Jack and his family go to Yellowstone National Park, where Jack's mother is investigating the report that wolves reintroduced to the park have killed a dog there.

While she studies condors in the Grand Canyon a scientist's life is threatened, and the strange teenage computer whiz in her family's foster care might be involved.

While at St. John National Park in the Virgin Islands for a seminar on coral reefs, the Landons help a wealthy thirteen-year-old to find his birth mother, who he believes is in danger.

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.

While their parents study why wolverines are disappearing from Alaska's Denali National Park, Jack and Ashley are stranded in a remote area with their mysterious new foster brother when a hit man's bullet triggers an avalanche.

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.