Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and are going to visit their cousins Joe and Alice.
To the children's delight, Joe and Alice live near a wonderful amusement park. The park holds everything the Boxcar Children could ask for -- a beautiful merry-goround, lots of rides and games, all the cotton candy they can eat ... and a mystery!