Evie is an adventurous, book-loving sixth grade girl who shows courage and resourcefulness in her efforts to help her friends, save her school from disaster, and find the identity of her real parents.
She loves Ferngarden School, a small independent middle school set near a river in a small, working-class neighborhood. She finds and furnishes an attic hideaway there where she loves to read and eavesdrop on the teachers.
But just before opening day the teachers find a strange infestation of copperhead snakes in the school and on the grounds. Evie learns that if the school does not open on schedule, the property goes back to the estate of the original donor. The heir is a conniving developer who is trying to take over the neighborhood.
After desperate but failing efforts to open the school on time, a court hearing puts the ownership of the school on trial. Further eavesdropping by Evie uncovers the mystery, but will she be able to save the school?