Judy is thrilled when she learns that her old friend, Dora Scott, is returning to Farringdon. The girls plan a huge welcoming party for Scottie at the railroad station, but Judy realizes that their plans were a mistake when she sees Scottie's reaction. Scottie is tired and impatient and has her little sister Carol in tow. Carol is a very unusual child who is unresponsive to all sound except music and whistling. Scottie expects Judy to help her find a way to help Carol. Judy is uncertain how to proceed and feels that Scottie expects too much of her. Judy also has two other mysteries to solve. Something mysterious is happening at the Chinese laundry in Farringdon, and objects keep disappearing from the houses on Grove Street. How Judy solves Carol's problem and how it relates to the other mysterious happenings makes for a thrilling story.