Novel: The Sign of the Four

Summary
"The Sign of the Four" opens with Dr. John Watson called to the matter of a young client, Mary Morstan, who arrives with an intriguing history and little more than a single, unanswerable question. Ten years earlier her father, Captain Arthur Morstan, vanished without explanation, and in the years since Mary has received one perfect pearl each year from a mysterious benefactor. When a final anonymous letter demands that she come to a meeting to learn the truth, she turns to Sherlock Holmes and Watson. Holmes rapidly sorts the facts and reconstructs a tale whose roots reach deep into Britain's imperial past: a secret stolen treasure, a pact among four men made abroad, and a chain of betrayals that has left a single surviving claimant nursing a fierce, private grievance.
Holmes and Watson trace the case to the Sholto family and to Pondicherry Lodge, where one of Major Sholto's sons, Thaddeus, reveals the existence of the Agra treasure and the fatal quarrel that broke the compact among the original four. The investigation draws the detectives into a web that includes Jonathan Small, a scarred, wooden-legged man who had once been involved in the theft and who now claims to have been betrayed and left to prison; Small has an unusual and frightening ally in Tonga, a small, savage islander whose presence brings an exotic and brutal element to the pursuit. The plot accelerates into violence and a desperate river chase on the Thames, where Holmes's methodical cleverness and Watson's courage combine to confront the fugitive conspirators and expose the chain of events that led to the long, secreted treasure.

Themes and Aftermath
The story combines a tightly plotted detective narrative with Victorian-era attitudes toward empire, race, and honor. The exotic backstory, set partly in India and the Andaman islands, adds atmosphere and motive, but it also brings troubling racial caricature in the depiction of Tonga, reflecting contemporary prejudices that modern readers find uncomfortable. Doyle balances the sensational elements with Holmes's forensic brilliance: small clues, keen observation, and psychologically acute deductions drive the unraveling of a case that at first seems to be a straightforward request for explanation but turns out to be a study of greed, loyalty betrayed, and the consequences of colonial greed.
Watson's narration also foregrounds a domestic strand: his growing affection for Mary Morstan and the personal changes that her presence brings to his life. The tale ends with the immediate puzzle resolved and justice largely served, but with some moral ambiguities intact, treasure and culpability, love and loss, are all complicated by the characters' past choices. "The Sign of the Four" remains a compelling example of Doyle's flair for plot and atmosphere, showcasing Holmes at the height of his powers while reflecting the era's wider anxieties about Britain's imperial reach and the costs it imposed on individual lives.