The one unsolved mystery from Judy's childhood is that of the haunted fountain on the Brandt estate. Judy visited the fountain one time and it told her to make a wish. She never did learn how the fountain spoke.After relating the story to Lois and Lorraine, the three girls visit the Brandt estate to see the fountain. After ignoring a ""No Trespassing"" sign, they are confronted by two men who threaten them. The girls leave but sneak back so they can visit the fountain. Judy finds a diamond in the fountain and wonders how it came to be there. Something is also bothering Lorraine, and it is apparently connected to the mysterious events at the Brandt estate. Judy wants to help Lorraine, but her biggest obstacle is getting proud Lorraine to speak about her problems.