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.
The Alden children suspect that the other guests are somehow involved when things begin to disappear at the bed and breakfast where they are staying in Washington, D.C.
When Cam Jansen and her friend Eric uncover a mystery while selling fudge door-to-door to raise money for the local library, Cam uses her photographic memory to foil a crime.
Reports of zombies and grave-robbers alarm the people of a Louisiana swampland village, but Ruth Rose, Josh, and Dink begin to suspect that the supernatural may not be the cause of the eerie occurrences.
In the midst of a series of unexplained accidents and mysterious coincidences, sixth-graders Calder, Petra, and Tommy lead their classmates in an attempt to keep Frank Lloyd Wright's famous Robie House from being demolished.