"The Sign of the Four" by Arthur Conan Doyle is a detective novel written during the late 19th century. It features the iconic character Sherlock Holmes, along with his loyal companion Dr. John Watson, as they are drawn into a complex mystery involving a missing treasure, a disappearance of a father, and a series of puzzling pearls sent to a young woman. The novel intricately weaves elements of intrigue, adventure, and crime, showcasing Holmes's exceptional deductive reasoning. The opening of the novel sets a captivating tone as Dr. Watson describes the troubling habits of his friend Sherlock Holmes, particularly his use of cocaine to stimulate his mind.