In this, the second book of the Ruth Fielding series, Ruth goes to boarding school with her best friend Helen. When they get there, Ruth starts her own sorority called the SweetBriars for the new girls. Her sweet group of girls conflicts with the two other sororities the Upedes and the Fussy Curls. In the midst of settling in to the new place, there is a campus rumor about a legend of the marble harp playing ominously at night. But when the French teacher is in a fright, will Ruth be able to solve this mystery?

The Ruth Fielding series has influenced several other major series that came later, including Nancy Drew, the Dana Girls, and Beverly Gray. (Summary by Charlotte Duckett and Kimberly Krause)