The Adventure of the Red Circle by Arthur Conan Doyle

A worried landlady reports her mysterious lodger’s strange behavior—silent days, nocturnal movements, and hidden messages. Holmes’s investigation uncovers a tangled story of escape from a criminal syndicate, secret codes, and protection of a woman from an assassin. The plot unspools with quiet tension and surprise twists. A seemingly minor case leads to international intrigue and deadly threats. It’s a tale of courage, loyalty, and justice beneath the surface of urban anonymity.