He´s an intelligent man. He was once rich and is now poor. His wife loved him once, but she doesn´t love him now. And he´s thirty or forty years old. One look at an old hat, and Sherlock Holmes can tell you a lot about its owner. He sees - and thinks - a lot more than the people around him, and when a beautiful blue diamond disappears, Sherlock is the only man in London who can find it.