The Moonstone is a Victorian mystery novel by the English writer Wilkie Collins. It was originally published in serial installments between January and August 1868. The Moonstone is sometimes considered one of the first detective novels in English, with its suspenseful and dramatic plot building on the success Collins had achieved with an earlier mystery novel, The Woman in White (1860). Throughout The Moonstone, Collins explores the themes of Public Reputation Versus Inner Nature, The Tensions Between Empirical Evidence and Faith, and The Unreliability of Witnessing and Memory.

This guide uses the 2001 Modern Library edition.

Content Warning: The source text contains references to death by suicide and Victorian-era prejudices surrounding Indian religion and culture.

Plot Summary

In 1799, an Englishman named John Herncastle steals a large diamond (known as “the Moonstone”) from India and takes it back to England. The diamond is a venerated religious object that is rumored to be closely guarded by three priests; it is said that a curse will befall anyone who steals the diamond. When Herncastle dies in 1848, he leaves the diamond to his niece, Rachel Verinder. Many people are confused by this gesture, since Herncastle was not on good terms with his sister (Rachel’s mother). Herncastle’s nephew, Franklin Blake, is hesitant about presenting the diamond to his cousin Rachel, with whom he is also in love. In the lead-up to Rachel’s 18th birthday (the day that she is supposed to receive the diamond), Franklin’s fears are exacerbated by the presence of three Indian men who seem to be lurking near Rachel’s home in Yorkshire.

Nonetheless, Franklin gives Rachel the diamond on her birthday, June 21,1848. She is delighted, and locks up the diamond in a sitting room adjoining her bedroom. The next morning, the diamond has inexplicably vanished. A police detective named Sergeant Cuff begins investigating the case. Cuff’s investigations reveal that whoever stole the diamond likely would have stained their clothing with some wet paint. However, no one can find the incriminating items of clothing. Suspicion seems to point to a young servant girl named Rosanna Spearman. Rachel herself is also acting very strangely, particularly toward Franklin Blake.

Rachel’s cold and aloof behavior eventually drives Franklin to leave England. Meanwhile, Rosanna dies by suicide. Rachel and her mother move to London, and consider the case to be closed, accepting that the diamond won’t be found. However, Cuff predicts that the case is not over: He thinks that someone—likely Rachel herself—has taken the diamond to London and pawned it to a man named Septimus Luker. Since the three Indians are determined to get their hands on the diamond, Cuff suspects that further events will unfold around June 1849: At this time, whoever pawned the diamond will come to reclaim it and the Indians will have the opportunity to try to seize it, as until then the diamond has been securely stored in a London bank.

In London, Rachel spends more time with her other cousin and suitor, Godfrey Ablewhite, who was also present at the Verinder house on the night the diamond was stolen. When Godfrey proposes, Rachel accepts, while openly admitting that she is in love with someone else. However, shortly thereafter, Rachel’s mother dies, and Rachel and Godfrey amicably but mysteriously break off their engagement. In the spring of 1849, Franklin Blake returns to England to attempt to reconcile with Rachel, but she still refuses to have anything to do with him, spurring Franklin to solve the mystery of the diamond. He returns to Yorkshire to investigate, and learns that before her death, Rosanna Spearman left instructions for him, which lead him to a stained nightshirt that Rosanna carefully hid. Shockingly, the nightshirt implicates Franklin himself as the thief: Rosanna concealed the evidence because she was in love with him, but died by suicide when he kept ignoring her in the aftermath of the crime.

Franklin finally confronts Rachel, who explains that she saw him take the diamond. She has been furious with him for lying ever since, but she has also concealed what she knows about the theft. Franklin is baffled and eventually begins collaborating with Ezra Jennings, the assistant to the local Yorkshire doctor. Since Jennings regularly consumes opium due to a painful disease, he is able to theorize that Franklin may have unwittingly stolen the diamond while under the influence of opium. Together, Franklin and Jennings uncover evidence that on the night the diamond was stolen, the doctor (with help from Godfrey Ablewhite) secretly gave Franklin opium.

This explanation leads to a reconciliation between Franklin and Rachel, but it is still unknown what happened to the diamond after Franklin took it. Franklin keeps a close eye on the London bank where the diamond is being held; he and Cuff trace a man who claims the diamond, but find him murdered the next day. The man turns out to be Godfrey Ablewhite in a disguise. Godfrey has presumably been murdered by the three Indians who were also following him, who have now seized the diamond. In the wake of Godfrey’s death, the whole story is finally revealed: After Franklin took the diamond in his opium-induced trance, he ran into Godfrey and handed it to him. Godfrey was tempted by the diamond, since he was badly in debt and needed money. When he realized that Franklin had no memory of what happened, Godfrey kept the stone and pawned the diamond in London.

Rachel and Franklin marry and live happily together. Further reports eventually reveal that the three Indians did indeed steal back the diamond from Godfrey and successfully returned it to India, where it is restored as a religious artifact.