A newspaper reporter challenges Nancy to solve a weird mystery involving an amusement park merry-go-round. Why does the carousel light up in the middle of the night and begin revolving and playing music when no one is around?
In search of an answer, Nancy finds herself matching wits with two clever criminals — and tries to hunt down one of them in the park’s haunted house. Meanwhile, a teenage heiress seeks the young detective’s help deciphering a strange flower riddle that her father presented to her just before he died. The plot thickens when a woman who may hold a vital clue to the mystery suddenly disappears!
With the help of her friend, Ned, Nancy sets out to catch the sinister culprits, but discovers too late that she and Ned are the ones really caught in a trap!