Chapters 9-12: The Resolution
Chapter 10: The Thames Chase
The Thames chase is the novel’s most dramatic set piece. Holmes hires a police launch and, with Watson and Athelney Jones aboard, pursues Jonathan Small and Tonga down the river at night. Doyle fills the scene with vivid sensory detail: the dark water, the throbbing engines, the distant lights of London’s docklands. Watson describes how they “flashed past barges, steamers, merchant-vessels” while the engines throb “like a great metallic heart.”
The chase serves multiple purposes. It provides thrilling action after the intellectual puzzle of the earlier chapters. It moves the story from the drawing rooms of Upper Norwood to the industrial Thames — from the respectable face of Victorian London to its working waterfront. And it ends in violence: Tonga fires a blowpipe dart at the pursuers, narrowly missing Watson. Holmes and Watson fire at the same instant, and Tonga is shot and falls into the river, where his body is never recovered.
During the chase, Tonga raises his blowpipe at the police launch. Holmes and Watson fire at that instant, the dart whizzes between them, and Tonga falls dead into the Thames. Jonathan Small, realising he cannot escape, throws the Agra treasure overboard piece by piece into the river. The treasure that drove the entire plot is lost forever.
Tonga’s Death and Victorian Racial Attitudes
Tonga’s death is troubling from a modern perspective. He is shot without hesitation and his body sinks unrecovered into the Thames — no character mourns him. Doyle describes Tonga using language that reflects deeply racist Victorian attitudes: he is called a “savage,” “unhallowed dwarf,” and compared to an animal. Holmes earlier deduced his origins from a colonial gazetteer that describes the Andaman Islanders as “naturally hideous” and “fierce, morose, and intractable.”
In the exam, you should acknowledge that Doyle’s portrayal of Tonga reflects the racial prejudice of his era. Victorian Britain widely believed in a racial hierarchy that placed white Europeans at the top. Tonga is not given a voice, a backstory, or any humanity — he exists in the novel only as a weapon and a threat. Jonathan Small, by contrast, is given a full confession and the chance to explain himself. This disparity reveals whose stories Victorian society valued and whose it erased.
Chapter 12 is Jonathan Small’s extended confession, narrated in his own voice. Small was a young British soldier serving in India when he lost his leg to a crocodile. During the Indian Rebellion of 1857, he was posted to guard the Agra fort. Abdullah Khan, one of the Sikh soldiers on guard with him, offered Small a share of a vast treasure in exchange for his help in ambushing a merchant. Small swore the pact first — the “sign of the four” — with the three Sikhs, and only then did they murder the merchant. All four names were written on the plan of the fort.
Small was caught and imprisoned in the Andaman Islands, where he befriended Tonga. He revealed the treasure’s location to Major Sholto and Captain Morstan in exchange for help escaping, but Sholto betrayed him and took the treasure. Small spent years plotting revenge. His confession is sympathetic in places — he feels genuinely wronged by Sholto — but he also participated in murder and shows no remorse for the merchant’s death.
The Agra Treasure: Greed and Its Consequences
The Agra treasure is the engine of the entire plot. Every crime in the novel flows from it: the original murder of the merchant, Small’s imprisonment, Sholto’s betrayal, Morstan’s death, Bartholomew’s murder, and the Thames chase. Yet the treasure itself is ultimately worthless — Small throws it into the river rather than let anyone else have it. “It is my treasure; and if I can’t have the loot I’ll take darned good care that no one else does,” he says.
Doyle uses the treasure to explore the theme of greed. Everyone who touches the treasure suffers: the original merchant is murdered, the four conspirators are imprisoned, Sholto dies tormented by guilt, Morstan dies in an argument over it, Bartholomew is murdered for it, and Small loses both the treasure and his freedom. The moral is clear: the treasure brings nothing but suffering.
The Agra treasure destroys everyone who pursues it. The merchant is murdered for it, the four conspirators are imprisoned, Sholto and Morstan both die because of it, Bartholomew is killed, and Small throws it into the Thames. Doyle’s message is that greed corrupts and that stolen wealth brings only suffering.
Chapters 11–12: The Ending — Love and Cocaine
With the treasure lost, Watson realises Mary Morstan will remain poor — which removes the class barrier to their relationship. He proposes and she accepts. Watson’s joy contrasts sharply with Holmes’s reaction. Holmes shows no interest in the romance and, with the case solved, returns immediately to his cocaine. The novel ends as it began: Holmes reaching for the syringe.
The novel’s cyclical structure is significant. It opens with cocaine and closes with cocaine, suggesting that Holmes’s restlessness cannot be permanently satisfied. Each case is only a temporary reprieve. The structure also contrasts Holmes and Watson: Watson moves forward (marriage, emotional fulfilment) while Holmes remains trapped in a cycle (case, cocaine, case). This ending raises questions about whether Holmes’s genius is a gift or a burden.
The contrast between the two endings — Watson’s romantic happiness and Holmes’s solitary cocaine use — mirrors the novel’s dual structure throughout. Watson represents emotion, warmth and human connection; Holmes represents intellect, isolation and obsessive focus. Doyle suggests that neither approach alone is complete.
The resolution of The Sign of Four is deliberately bittersweet. Justice is served (Small is captured), the mystery is solved, and Watson finds love. But the treasure is lost, Tonga is dead, Holmes is back on cocaine, and the underlying causes — imperial greed, social inequality — remain unchanged. Doyle does not offer a neat, triumphant ending.