Red Leech by Andrew Lane

Red Leech : Paperback : Pan MacMillan : 9781447265597 : 1447265599 : 10 Jun 2014 : Crack the case with the world's most famous detective! But before he became the great detective, who was young Sherlock Holmes? The second book in a series of mystery adventures featuring a teenage Sherlock and endorsed by the Conan Doyle Estate.