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.

While vacationing at a friend's country home, the four Alden siblings try to find a long-missing, priceless brooch and investigate the existence of a ghostly stream.

While they are visiting bayou country, Benny sees something in the swamp that no one can explain, and he's not the only one to see it.

Benny wants adventure and finds it as he and the other Alden children help uncover the plan of those who would prevent ballooning from coming to Lloyd's Landing.

Henry, Jessie, Violet, and Benny have never been to a drive-in movie theater before, but they_re visiting a friend who owns one. The children love to eat popcorn in the car and watch movies under the stars. But strange pranks are disrupting the fun_one night the sound system starts playing loud music during the movie, and a couple of the theater employees seem to be hiding a secret. Then, late at night, a ghost is seen walking around the empty grounds...

When their grandfather buys a bookstore at auction in New Orleans, the Alden children help clean it up and discover that several people seem to be obsessed with the store and its contents.