Secrets of the Stone, The Adventures of Lottie Lipton

Welcome to the British Museum, home to Lottie Lipton: nine-year-old investigator extraordinaire! There's been a break-in at the British Museum and someone's after the priceless Rosetta Stone. When Lottie spots a hidden message, she and her friends might be on the verge of a great discovery. Can they follow the clues, and what will they find if they do?