Key themes
- The locked-room mystery as a structure of revelation and justice
- Holmes as pure intellect — and Watson as the humanising observer
- Empire and its crimes — the Indian treasure and its bloody history
About this book
Sherlock Holmes and Dr Watson are engaged by Mary Morstan to investigate the mysterious death of her father and a series of pearls left for her by an unknown benefactor. The case leads to a stolen Indian treasure, a pact of vengeance and one of Holmes's most elaborate investigations. The novel also introduces Watson's courtship of Mary, who becomes his wife.
Published in 1890, The Sign of Four introduced Irene Adler, established Holmes's cocaine use, and showed Watson falling in love with Mary Morstan. It is one of the four Sherlock Holmes novels.
Discussion questions
- The novel introduces Holmes's cocaine habit alongside his intellectual gifts. What is Doyle doing by showing both — and does the addiction serve the characterisation?
- The Sign of Four involves Indian treasure stolen during the Mutiny of 1857. How does Doyle treat the colonial context — and what does the novel reveal about its era's assumptions?
- The relationship between Holmes and Watson is the book's emotional centre even when Holmes seems to deny the importance of emotion. How does Doyle develop the partnership?
- Holmes explains his reasoning at length. How does Doyle make these expositions dramatic rather than merely clever?
- The Sign of Four is a GCSE set text. What does it offer young readers — and what do teachers need to address about its historical assumptions?
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The Sign of Four appears on the following curriculum reading lists.
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