Chapters 1-5: The Mystery Begins
Chapter 1: Holmes, Watson and Cocaine
The novel opens not with a crime, but with a character study. Sherlock Holmes reaches for his hypodermic syringe and injects a “seven-per-cent solution” of cocaine. Watson watches with open disapproval, calling it a “pathological and morbid process.” This opening immediately establishes two things: Holmes’s extraordinary mind needs constant stimulation, and Watson serves as both narrator and moral conscience.
Holmes explains: “My mind rebels at stagnation. Give me problems, give me work.” Without a case, his brilliance turns inward and becomes destructive. Doyle uses this opening to show that Holmes is not a conventional hero — he is flawed, restless and potentially self-destructive. The cocaine is not glamorised; Watson’s medical perspective ensures the reader understands the danger.
Holmes tells Watson: “My mind rebels at stagnation.” He uses cocaine to escape boredom when no case occupies his intellect. Watson, as a doctor, calls it a “pathological and morbid process” — Doyle uses Watson’s disapproval to show the habit is harmful, not heroic.
Holmes also demonstrates his deductive method by analysing Watson’s pocket watch. From scratches, dents and a pawnbroker’s mark, Holmes deduces that Watson’s late brother was an alcoholic who squandered his inheritance. Watson is hurt and angry, revealing tension beneath their friendship. This scene establishes that Holmes’s deductions, while brilliant, can be cold and invasive.
Chapter 2: Mary Morstan’s Case
Governess Mary Morstan arrives at Baker Street with a compelling mystery. Her father, Captain Arthur Morstan, vanished ten years ago after returning from India. Since then, she has received an anonymous pearl every year, and now an unsigned letter invites her to a meeting. Holmes is immediately energised — he has a problem to solve.
Mary is presented as composed, brave and practical. Watson is immediately attracted to her, noting her “sweet and amiable” expression. Doyle uses Watson’s romantic interest to create a secondary plot thread alongside the mystery. Importantly, Watson notes that if the treasure is found, Mary will be wealthy — and as a man of modest means, he feels he cannot honourably declare his feelings to a rich woman. This reflects Victorian attitudes to courtship and class.
The trio travel through foggy London to meet Thaddeus Sholto, one of the sons of Major John Sholto. Thaddeus is a memorable comic creation — nervous, theatrical, obsessed with his own health, and surrounded by Eastern art and luxury. He reveals the backstory: his father, Major Sholto, had been Captain Morstan’s fellow officer in India. They both knew of the Agra treasure. Major Sholto stole the treasure for himself, and Captain Morstan died of a heart attack during an argument about it.
Thaddeus has been secretly sending Mary the pearls out of guilt. He explains that his twin brother, Bartholomew, has now found the treasure hidden in the attic of their family home, Pondicherry Lodge. He invites them to claim Mary’s share.
Chapter 5: The Horror at Pondicherry Lodge
When they arrive at Pondicherry Lodge, the housekeeper is frantic — Bartholomew Sholto’s room is locked from inside. Holmes and Watson break in to find Bartholomew dead, his face frozen in a terrible grin. A poison dart is embedded in his scalp, and the treasure chest is empty. On the table is a card reading “The sign of the four.”
This is the novel’s most Gothic moment. Doyle uses horror conventions — the locked room, the distorted corpse, the mysterious calling card — to heighten tension. The locked-room mystery was a popular device in detective fiction, creating an apparently impossible crime that only Holmes’s logic can solve. Watson describes Bartholomew’s face as wearing a “horrible smile, a fixed and unnatural grin” — the poison causes involuntary muscle contraction, but the effect is deeply unsettling.
At Pondicherry Lodge, Holmes finds three crucial clues: a small footprint (Tonga), the marks of a wooden leg (Jonathan Small), and spilled creosote from a cracked carboy, which Tonga treads in and Toby can follow. The card reading “The sign of the four” connects the murder to the original pact over the Agra treasure in India.
The locked-room mystery was a staple of Victorian detective fiction. Poe used it in ‘The Murders in the Rue Morgue’ (1841). In The Sign of Four, Bartholomew’s room is bolted from inside, yet someone has entered, murdered him, and stolen the treasure. Holmes solves it by looking upward — the killer entered through a trapdoor in the roof. This demonstrates Holmes’s ability to see what others miss, and Doyle’s skill in using genre conventions to create suspense while ultimately providing a rational explanation.
How Doyle Builds Suspense in Chapters 1–5
Doyle structures these opening chapters as a crescendo. Chapter 1 is slow and domestic — two friends in a sitting room. Chapter 2 introduces the mystery. Chapter 3 takes them through the fog to a secret meeting. Chapter 4 raises the stakes with Thaddeus’s revelation. Chapter 5 delivers the shock of murder. Each chapter increases the tension, drawing the reader deeper into the plot. Watson’s first-person narration limits what the reader knows, creating suspense because we discover clues at the same pace as Watson — always one step behind Holmes.