The case of the missing marquess

The book is about a young girl called Enola, which backwards spells alone. After her mother goes missing, her 2 brothers, the famous detective Sherlock Holmes. And her eldest brother, Mycroft. They both want Enola to go to finishing school while Sherlock works out the case. She ends up escaping them and meets up with The Viscount Tewkesbury, Marquess of Basilwether. He has also run-away. They end up going on the journey to London together. Soon after going their separate ways, someone trying to kill Tewksbury. Enola defeats them and continues going to find her mother.