In The Moonstone book how does the Prologue and the Epilogue help shape the structure of the novel?

The prologue of The Moonstone prepares us for both the historical background of the novel and the narrative technique. The setting of the opening and closing of the novel is India—the prologue is specifically about events on Indian soil, as well as being itself "written in India." Though the novel will follow the theft of the diamond from a household in England, the prologue reminds us that the diamond was stolen first and foremost from Indians by an Englishman. The Battle of Seringapatam is an actual historical event in the British occupation of India. The battle is significant because it reinforced the predominance of the East India Company at the time and, subsequently, British sovereignty in India throughout the nineteenth century when Wilkie Collins was writing. The Prologue is unequivocal about the unethical quality of John Herncastle's violent acts and theft of a spiritually significant object, and this can be read, by extension, as a condemnation of British treatment of occupied India.

Both the prologue and the opening chapters of the novel call attention to themselves as written documents. The Moonstone has no single narrator, and no omniscient, third-person narration that can reveal everyone's thoughts. Instead, the novel consists of over a dozen individual testimonies written by various characters involved with the diamond or the Verinder family. These characters, in turn, rely on other written documents that are often reproduced within the narrative (though some are not reproduced, as is the case with Penelope's diary). Franklin Blake, nephew to Lady Verinder, serves as the "editor" of the various testimonies and the force behind the project of taking them all down in writing. Blake suggests "we should all write the story of the Moonstone in turn—as far as our own personal experience extends and no farther." This technique of narration is well suited to the genre of detective fiction, whereby more and more information is gathered through various witnesses, and all cannot be revealed to us at once.

The city in which Murthwaite watches the stone restored in the novel The Moonstone is the same city from which the diamond was first stolen in the eleventh century by "the Mohammedan conqueror, Mahmond of Ghizni," as both the prologue and epilogue attest.

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The epilogue commences with the reports from Sergeant Cuff's man and the steamboat captain regarding their respective failures to apprehend the Indians and the diamond. Yet these failures seem unimportant once we read Mr. Murthwaite's concluding narrative, which depicts the diamond's return to India as a just homecoming. Murthwaite is back in India, as a spy of sorts—he pretends to be a fellow Indian Hindu—and reports back to England on the events and people there. His narrative ensures that the story of the theft of the Moonstone is framed on either side with a narrative that places the Moonstone in India. This larger frame narrative encourages us to see the theft of the Moonstone by Godfrey Ablewhite as a replication of the theft of the Moonstone from India by John Herncastle in 1799. This last theft can then also be read as a miniature version of the greater exploitation of India by the English crown. These thefts of the Moonstone can also be read as simply part of the long, dangerous history of the valuable stone. The city in which Murthwaite watches the stone restored is the same city from which the diamond was first stolen in the eleventh century by "the Mohammedan conqueror, Mahmond of Ghizni," as both the prologue and epilogue attest.

The ceremony which Murthwaite witnesses is not only the celebration of the restoration of the Moonstone to the Hindu idol of the Moon god, but also the dramatization of the sacrifice that the three Hindu high-caste Brahmins made to retrieve the diamond. Because they abandoned their high-caste, the Brahmins must face cleansing—a cleansing which will last the rest of their lives. They have become permanent exiles, sent to wander on pilgrimage in separate directions. The selfless sacrifice made by the Indians is part of a larger theme of self-sacrifice in The Moonstone, which also includes Rachel's sacrifice of her reputation for Franklin, and Jennings's sacrifices for Mr. Candy, Franklin, and Rachel.