The Alden children stumble upon a mystery when they enter their dog, Watch, in a contest that could lead to fame and fortune, but where things keep going wrong.
The Alden siblings tackle a series of Halloween mysteries, where they investigate a pumpkin-headed ghost on a friend's farm, examine a zombie sighting in the woods, and determine if their boxcar home is haunted.
While exploring the caves around Dragon's Mouth Cavern, a series of unusual and somewhat frightening events convinces the Alden children that someone does not want them around.
The Alden children travel on a Mississippi paddle-wheel steamer to visit an old family friend in his cabin near Hannibal, Missouri, and try to discover who is responsible for the mysterious activities near the house.
When a local radio station holds a detective contest, the Aldens enthusiastically sign up, but when some of the clues turn out to be fake, they have a real mystery on their hands.
When the Aldens agree to watch the house of a local author who has written a book about a vampire, they end up investigating activities that are suspiciously similar to those in his book.
During a trip to Oregon, the Aldens are astonished when Watch discovers a backpack filled with valuables, a finding that compels them to learn what happened and return the backpack to its rightful owner.
When the Alden children's dog, Watch, finds a box in the park with a note inside, they are introduced to the hobby of geocaching and eagerly join the local club, but it looks like a thief may have joined as well.
A family, snowbound in a vacation cabin, discovers adventure in surrounding wild life, three children they find in the snow, and a search for a lost recipe.
While visiting the Diamond Drive-In with their grandfather, the Boxcar Children investigate a series of pranks and ghost sightings at the outdoor theater.
The Alden children are helping grow vegetables in a restaurant owner's garden, but when the tomato plants are moved from their original position the children begin to suspect that the move is connected to a robbery at the local bank.
A friendly writer with a metal detector, the mysterious inhabitants of a tower house, and the discovery of a locket in the sand are ingredients for the Aldens' latest mystery.