When the Alden children join a group of volunteers to fix up an old house for senior citizens, they try to explain the puzzling behavior of their coworkers as well as investigate some unusual events.

While visiting a recent purchase of Grandfather's, a ghost town in the Rocky Mountains, the Aldens encounter a mystery involving a run-down motel and a woman who may be a ghost.

People line up around the block to buy Mama Tova's cupcakes. But who could be trying to steal her secret recipe? The Boxcar Children follow clues to a cupcake contest, where they must use their mystery-solving skills to find a thief.

The Aldens participate in a three-day bicycle ride and soon find that someone seems to be intent on keeping others from completing the event.

While canoeing and backpacking near Timberwolf Lake, the Aldens receive strange warnings to stay away from the area and stumble upon clues to a missing cache of stolen coins.

When they take their dog, Watch, for obedience training, the Alden children discover that some of the dogs in the class have vanished and decide to try to solve the mystery of their disappearance.

The Aldens are excited to meet their favorite celebrity-Walter the Cat, who makes the funniest videos on the Internet! And when this celebrity cat inherits a million dollars from his owner, he becomes even more famous! But someone seems to be angry about the will and is stealing things from Walters house. Is this cat too famous for his own good?

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.

The Alden children help out at the Greenfield Ice Cream Barn and while learning to make ice cream and create new flavors, they help solve a mystery before the Barn gets shut down.