With the wrapping up of the subplot involving their less lucky counterparts, Rachel and Franklin are now ready to marry. The Moonstone has maintained two plots throughout: the conventional marriage plot between Rachel and Franklin and the mystery plot revolving around the diamond. Betteredge's narrative, telling us of their marriage and the conception of their first child, wraps up the marriage plot, giving the novel a conventional end. The epilogue then wraps up the mystery plot.

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.