In the 1799 storming of Seringapatam, India, John Herncastle, a violent and cruel man, steals the sacred Hindu diamond called the Moonstone. The jewel had been taken years before from the forehead of the Moon-God in its Brahman shrine, and Herncastle's theft was only one of a series. Since the stone had first been stolen, three faithful Hindus followed its trail, sworn to recovering the gem and returning it to the statue of the Moon-God. Herncastle took the gem to England and now keeps it in a bank vault. He saves himself from murder by letting the Hindus know that if he were killed the stone would be cut up into smaller gems, thus losing its sacred identity. At his death, Herncastle leaves the jewel to his niece, Rachel Verinder. The stone is to be presented to Rachel on her birthday following her uncle's death. Young Franklin Blake, Lady Verinder's nephew, is asked by Herncastle's lawyer to take the gift to his cousin's home several weeks before the event, but he barely misses death at the hands of the Hindus before reaching his destination. On the advice of Gabriel Betteredge, the Verinders's old family servant, Franklin puts the gem in the vault of a bank nearby until the birthday arrives, as the Hindus had been seen in the neighborhood. Upon meeting, Franklin and Rachel fall in love. Guests begin to arrive for the birthday celebration, including Godfrey Ablewhite, a handsome and accomplished charity worker; Dr. Candy, the town physician; and Mr. Bruff, the family lawyer.