The Sign of the Four (1890) is the second novel by Arthur Conan Doyle featuring Sherlock Holmes. The story begins when Mary Morstan seeks Holmes's help after receiving anonymous pearls and a cryptic note linked to her father's mysterious disappearance. The investigation leads Holmes and Watson through London's foggy streets into a tale involving a hidden Indian treasure, a secret pact among four convicts, a one-legged man named Jonathan Small, and his deadly companion Tonga. The novel explores themes of greed, colonialism, and betrayal, while also introducing Watson's romance with Mary Morstan, adding emotional depth to this classic detective adventure.
