The action of ‘The Sign of the Four’ takes place in just four days as Holmes is introduced to the case, investigates it and solves it. This short time span ensures that the pace is swift to engage the reader. However, there are several recounts of events that took place years before Holmes and Watson start investigating the case, and these recounts by different characters add layers of interest to the straightforward linear plot.

• Sherlock Holmes and Dr Watson talk in their flat in 221B Baker Street. Their conversation helps introduce the reader to their characters.

• Miss Morstan arrives, seeking Holmes’ help in her father’s disappearance. She tells the story of how a pearl is sent to her every year by an unknown person who now requests a meeting with her. Holmes accepts the case.

• Holmes, Watson and Miss Morstan meet a coachman who takes them through the London streets to the house of Thaddeus Sholto.

• Thaddeus Sholto reveals that he has been sending Miss Morstan the pearl every year.

• Thaddeus then recounts the story that his father, Major Sholto, told on his deathbed.

• Major Sholto’s story relates how Captain Morstan (Miss Morstan’s father) died. Sholto and Morstan argued over the division of a great treasure and Captain Morstan fell during a heart attack.

• Thaddeus then tells his listeners that he and his brother, Bartholomew, have been searching for the treasure and that his brother have just found it hidden within the roof at their dead father’s house- Pondicherry Lodge.

• Thaddeus takes Holmes, Watson and Miss Morstan to Pondicherry Lodge. It is a dark, sinister night and it turns out Bartholomew has been murdered and the treasure stolen.

• The police arrive, represented by the inspector Athelney Jones, and arrest Thaddeus for the murder. However, Holmes states that the real murderer is Jonathan Small, a man connected to Morstan and Sholto through the mysterious ‘sign of the four’ which is mentioned in letters and documents.

• Holmes and Watson search for clues at Pondicherry Lodge. Holmes finds a tiny footprint and concludes there are two murderers. A dog is used to track the murderers to the River Thames.

• Holmes finds out that his suspects are hiding on a river boat, the Aurora. He employs some street boys, the Baker Street Irregulars, to search London for the boat.

• Watson visits Miss Morstan and their relationship develops.

• They wait for news as to the whereabouts of the Aurora.

• Holmes does not sleep and becomes agitated at the lack of news.

• Holmes disguises himself as a sailor and looks for the Aurora himself.

• Athelney Jones turns up and admits that he has arrested the wrong man. He asks for Holmes’ help in finding the true culprit.

• Holmes returns, delighted that he has found where the Aurora is hiding. The police and Holmes join forces to catch the murderers.

•  The police boat chases the Aurora down the River Thames.

• Small’s accomplice, Tonga, is shot dead.

• Jonathan Small tries to escape but is caught.

• Watson takes the box of treasure to Miss Morstan. The box is opened and is found to be empty. Watson and Miss Morstan declare their love for one another.

• Watson returns to Holmes and the police. Small recounts his story about how he became involved with the Agra treasure. Small is taken away to await trial.

The structure of the novel is commented on within the character and theme pages that follow. Look out for:

• Foreshadowing – when clues are given about what will happen later in the novel.

• Juxtaposition – when an action scene is immediately followed by a calmer, more reflective scene.

• The subplot of the love story which weaves its way through the novel.