Amelia and William spend a lot of time at the library, and this is where they plan to spend most of the summer holidays. But things change quickly when an old piece of paper falls out of a book Amelia takes off a shelf. As they work together to solve the riddle on the paper, they begin an adventure across London in search of hidden treasure - but they are not the only ones looking for those jewels. Amelia and William must put their knowledge of London and British history to the test as they solve clues hidden around the city, and they need to think fast, because dangerous forces are closing in