The Case of the Cryptic Crinoline by Nancy Springer

Enola is the little sister of Sherlock Holmes, and she's hiding from him in the home of Mrs. Tupper. Mrs. Tupper receives a note telling her to deliver a "bird-brained" message from thirty-five years ago, but she doesn't know what it means. When she disappears the next day, fourteen-year-old Enola must investigate. The mystery brings back memories of the Crimean War and the work of Florence Nightengale. However, it also uncovers the secrets of spies during that time, and they're willing to do anything to keep them secret. Enola discovers she's being followed and that her own life may be in danger.

This mystery series is easy to follow, and it's interesting to see Sherlock Holmes' little sister as the main character. It's an unusual game of cat and mouse as she tries to investigate the crime while avoiding her brother. You' ll need to read the book to understand that situation. This story is able to stand alone in the series, although the disappearance Mrs. Holmes is a continuing mystery. The book has a little over one hundred pages, so it's a pretty quick read.