The hit BBC series "Sherlock" offers a fresh, contemporary take on the original Sir Arthur Conan Doyle stories, and has helped introduce a whole new generation of fans to the legendary detective. In this TV tie-in edition to the classic novel, Sherlock and Dr Watson receive a visit from Mary Morsten, who offers up a particularly cryptic puzzle for them to solve. Her father went missing six years ago and since then she has received a pearl for every year he has not re-appeared.