Henry, Jessie, Violet, and Benny discover the fun in geocaching as they make new friends and search for hidden boxes around town, but the group soon begins to suspect that one of their new friends may be a thief.

When the children uncover a strange puzzle in a friend's back yard, it's the start of a "spy game" leading to gold. But first they must make sense of an old photo and a riddle, and learn just who is behind this mystery within a mystery.

Taking a shortcut through the Greenfield Cemetery, the Aldens stumble across a local superstition which maintains that visitors are required to leave gifts or suffer the wrath of a malevolent ghost, a suspicious tradition that prompts the children to expose the truth.

The Aldens help out at a minor league stadium and investigate when it appears someone in the ballpark is stealing the home team pitcher's signals and relaying them to the batters of the other team.

The Aldens are playing a test version of their favorite game: Ringmaster. But, the characters in the game are giving them strange clues! Is someone using the computer game to tell them something is wrong?

The growling bear mystery: The Aldens love exploring the many hiking trails around Yellowstone, especially Lost Cabin Trail. But suddenly, the trail is closed because of bear activity, and then the map disappears! Could someone be trying to keep the Aldens away from the trail? It's a mystery -- and the Boxcar Children are going to solve it! The mystery of the lake monster: When the Aldens arrive at Lake Lucille, they're excited to explore the forests...