Ideal for intermediate learners of English looking to improve or practise their English. The book is filled with useful vocabulary that is carefully graded and easy to understand, it also comes with audio, so that you can listen to the story at the same time as reading. Miss Mary Morstan has a strange story to tell.Since her father disappeared, she has received a large pearl through the post on the same day. Who is sending them? And what about her father's paper with the words 'The Sign of Four' written on it?