Edith Lavell 
Mystery of the Secret Band [PDF ebook] 

Teenage detective Mary Louise Gay has cracked a few cases on her own, and her father — a skilled detective himself — has recognized her innate investigative talents. When he asks Mary Louise to help him get to the bottom of a series of thefts at a hotel, she jumps at the chance. Though written with younger readers in mind, The Mystery of the Secret Band is an engaging read for any fan of classic detective fiction.