This novel involves a secret pact made in India between four convicts, a lost treasure and a betrayal by a major that will be therefore killed. It also shows Sherlock’s drug addiction and is where Watson meets Mary Morstan, his future wife. Second Sherlock’s story, the plot is somewhat intricate but a real pleasure to read.
“Winwood Reade is good upon the subject,” said Holmes. “He remarks that, while the individual man is an insoluble puzzle, the aggregate he becomes a mathematical certainty. You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. So says the statistician.”