Mary Morstan은 아버지가 실종된 이후 항상 같은 날 우편으로 큰 진주를 받게 된다. 누각 보내는 것이며, 'The sign of Four'라고 적힌 아버지가 남긴 문서는 무엇을 의미하는는 것일까?
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, every year for six years. Who is sending them? And what about her father's paper with the words 'The Sign of Four' written on it?