Carolyn Keene 
The Ringmaster’s Secret [EPUB ebook] 

Nancy’s Aunt Eloise, aware of her niece’s current interest in learning horseback riding stunts, sends her a second-hand golden bracelet bearing charms of horses in all five gaits; a sixth charm is missing. Coincidentally, the Sims Circus, former employer of Nancy’s equestrian instructor, is coming to town. Nancy investigates the link between the unhappy circus star, young aerialist, Lolita, and her bracelet.

Lolita is the adopted daughter of the acting manager, Ringmaster Kroon, and his wife. Pietro, the young, handsome clown, tells Nancy Lolita has the missing charm from her bracelet. Nancy’s regular appearances at the circus, and her detective reputation brings the ire of Kroon. When a bareback rider is injured, Nancy is asked to join the show as her replacement.