The story chronicled in "The Moonstone" begins
with a letter telling how John Herncastle acquired the yellow diamond for which the story is named and brought it to England. During the Storming of Seringapatam (a battle during Britain's conquest of India), Herncastle participated in the raid of a temple dedicated to the Indian moon god. After killing the Moonstone's three guardians, he took the Moonstone from the forehead of a statue of the deity. However, with his final breath, one of the guardians cursed Herncastle, saying that the moon god's wrath would follow him and his family for as long as the Moonstone remained in his possession. Herncastle paid the Indian no heed and took the Moonstone back to England. He kept it until the day he died.
Skip ahead almost 50 years later. The story picks up with the narrative of Gabriel Betteredge, a servant in the household of Lady Verinder, sister of John Herncastle. It is a month before the birthday of Lady Verinder's daughter, Rachel. In honor of the upcoming occasion, Franklin Blake, Rachel's dashing young cousin, comes to visit, and he brings the Moonstone with him. Franklin tells Betteredge that John Herncastle's will stated that the Moonstone was to be given to Rachel
as an eighteenth birthday present upon his death. Betteredge tells him that no good could possibly come of that, and he's right. Upon Franklin's arrival, he catches the eye of Rosanna Spearman, one of the servants. Rosanna is a reformed thief that Lady Verinder hired in order to give her a fresh start. She falls in love with Franklin at first sight. Three Indians also begin to appear in the surrounding area, seemingly looking for something. Both Franklin and Betteredge believe that they are tracking the Moonstone but they have no proof to support that conviction. In the weeks leading up to Rachel Verinder's birthday, Rachel and Franklin start painting the door of her room and falling in love. Franklin adores her so much he even gives up smoking, spending a lot of agitated days and sleepless nights without any regrets on the part of his decision. About a week before Rachel's birthday, a strange man comes to see Franklin on matters of business. The nature of the business is unclear, but it causes a rift between Franklin and Rachel. They make up by the next day and the situation is forgotten. The day of Rachel's birthday arrives, and Franklin gives her the diamond in the presence of her other cousin, a Mr. Godfrey Ablewhite, who also had an interest in marrying her. Godfrey attempts to make Rachel a marriage offer shortly after she's given the diamond. She refuses. More guests arrive for the birthday dinner but the two that deserve to be noted are Mr. Candy, the town doctor, and Mr. Murthwaite, a renowned traveler who had been to India multiple times. Mr. Murthwaite informs Rachel that the Moonstone holds great religious value in India and it would be extremely dangerous to carry it in any foreign parts. The rest of the dinner conversation remains equally gloomy, Franklin gets into a heated argument with Mr. Candy, and Betteredge starts thinking the diamond might just be cursed after all. The evening's festivities (or lack thereof) are disturbed by the appearance of the three Indians, disguised as jugglers. Mr. Murthwaite was able to see through their disguise and he confides to Betteredge and Franklin that the three Indians are most likely high caste Brahmins (holy men) charged with bringing the Moonstone back to India. This greatly distresses Betteredge and Franklin, but Rachel is completely unperturbed. She chooses to keep the Moonstone in one of the cabinets in her room, without a lock.
The next morning finds the Moonstone, inevitably, stolen. The entire house is thrown into an uproar. Rachel refuses to allow anyone to see her and has frequent outbursts of anger and tears. The superintendent of the local police is called. After the superintendent makes a superb mess of the investigation by blaming all the wrong people for the theft, Sergeant Cuff, a detective, is called in from London. Upon arriving, Sergeant Cuff finds the new paint on Rachel's door had been smeared the night the Moonstone was stolen.
He wishes to check the linens of everyone in the house from Lady Verinder to the lowest servant. Everyone obliges except for Rachel, who flat out refuses. This leads the Sergeant to believe that Rachel is somehow responsible for the loss of the Moonstone. Rosanna Spearman also starts exhibiting some very strange behavior. She says some very cryptic things to Franklin concerning the loss of the diamond and also starts disappearing from the house at strange times. Sergeant Cuff orders the servants to let him know whenever Rosanna leaves the house so that he can keep an eye on her. Both he and Betteredge end up following her trail to Cobbs Hole, a tiny fishing wharf just down the beach from the Verinder household. They find out that Rosanna had become good friends with one of the fishing families, the Yollands. Upon her last visit, she had bought a metal box and a few lengths of dog chain from Mrs. Yolland and told her that she intended to leave the area. Sergeant Cuff deduces that Rosanna intends to hide something in the box and throw it into the patch of quicksand by the beach near the house. However, he does not believe it's the Moonstone. Upon his and Betteredge's return, they find out that Rachel intends to leave the house and visit her aunt the next day. This leads Sergeant Cuff to believe that Rachel has stolen her own diamond. The day that Rachel leaves, Rosanna also disappears. Sergeant Cuff and Betteredge set out to find her, but find only evidence that she had committed suicide by throwing herself into the quicksand. Once Lady Verinder finds out, she dismisses Sergeant Cuff on the grounds that the Moonstone will probably never be found. However, before Sergeant Cuff leaves, he tells Betteredge to expect three things to happen. First, he will hear from the Yollands since Rosanna had a letter delivered to them before her death. Second, he will hear about the three Indians again since they go where the Moonstone goes. Third, he will hear of the moneylender the Moonstone was pledged to (if it was pledged at all). Franklin also leaves to travel to other parts of Europe and put the entire incident from his mind. Shortly after Franklin leaves, Mrs. Yolland's daughter Lucy comes to tell Betteredge that she has a letter intended for Franklin that can only be given to him alone. A few days later, Betteredge receives news that a moneylender named Septimus Luker was having some troubles with three loitering Indians that simply would not leave him alone. So ends the first period.
The second period picks up with a narrative by Miss Drusilla Clack, one of Rachel's cousins who lives in London. Rachel and Lady Verinder
journey to London to take refuge from the Moonstone incident. Miss Clack is a member of one of the many charities that Godfrey Ablewhite heads and a very self-righteous Christian. She starts her narrative off with the story about how Godfrey was attacked and tied up in an upstairs apartment after receiving a letter asking for charity related help. He was unharmed and nothing was stolen but it still caused quite an uproar. The same fate befell Septimus Luker, the moneylender. However one bank receipt mentioning a valuable of great price had been stolen. After the incident, Rachel starts showing an increased interest in Godfrey, much to Miss Clack's chagrin (she has quite the crush on Godfrey). Miss Clack also finds out that Lady Verinder is suffering from heart disease and is likely to die soon. She names Miss Clack as one of the witnesses to the signing of the will. Mr. Bruff, Lady Verinder's lawyer and Miss Clack frequently butt heads over everything from theology to who really stole the Moonstone. Mr. Bruff suspects Godfrey while Miss Clack suspects Franklin. After the will is signed, Godfrey tries proposing marriage to Rachel again and this time she accepts. Before they can let Lady Verinder know of their plan, her disease takes her. Following her death, Rachel is sent to stay with one of her aunts in Frizinghall. After staying there for a while, she breaks off her engagement to Godfrey and leaves. So ends the second period.
The third period consists of a short narrative by Mr. Bruff. Shortly after Rachel and Godfrey announced they were going to be married, Mr. Bruff gets a call from a different law firm asking to see a copy of Lady Verinder's will. Mr. Bruff allows it but demands to know who's behind the order and why. The name the second law firm gives is Godfrey Ablewhite. It turns out that Godfrey had been having some money troubles and saw marriage to Rachel as an easy way out of them. Mr. Bruff alerts Rachel as quickly as he can and she breaks off the engagement almost immediately. About a week or two later he is visited by a man that appeared to be Indian. He asks about the customary length of time allowed for someone to pay back a loan. Mr. Bruff answers one year. He also has a conversation with Mr. Murthwaite about how and when the Indians will try to take the Moonstone back. Their conclusion is they will try to get the Moonstone a year after it was pledged to the bank, meaning in the summer of 1849. So ends the third period.
Franklin Blake steps up as a narrator for the first time in the fourth period. Since the events of the first narrative, he has been abroad. His father has since died, leaving him a great sum of money to pay off his debts. Franklin returns to England for the purpose of discovering what truly happened to the Moonstone and trying to clear his name with Rachel, who was hell-bent on blaming him for the whole mess. When he returns to the Verinder house, Betteredge informs him of the letter that Rosanna had left for him with Lucy. They pay the Yollands a visit the next day to retrieve it. The letter tells him to go to the quick sand and find the chain attached to the metal box hidden
beneath it. Franklin finds the box and inside is a letter and the paint-stained nightgown. It turns out the nightgown was his, however, there is one problem. Franklin has no memory of taking the Moonstone or even seeing it after Rachel put it away. The letter chronicles Rosanna's love for Franklin and how she was the one that first found the paint-stained night gown. Out of her love for him, she hid it and told no one, even though others suspected her of this theft. Franklin is greatly disturbed by the letter and the contents of the box, and try as he might, he simply could not remember anything between Rachel's birthday dinner and waking up the morning after. He decides to go to Mr. Bruff and ask him if there's any way he can talk to Rachel about what had happened. Mr. Bruff agrees to set up a surprise meeting. Once Franklin and Rachel meet up, she tells him, in a heated argument, that she saw him take the Moonstone from her room. Franklin doesn't understand how this is possible, but Rachel is adamant in her claim. Franklin leaves with more questions than answers. Upon returning to the Verinder house, he decides to have a talk with Mr. Candy, the doctor he had an argument with on the night of Rachel's birthday, to see if he remembers anything strange from that night. Unfortunately, Mr. Candy had become very ill since then and lost a good portion of his memory. His memory proves no better than Franklin's. However, Franklin has the good luck to meet Ezra Jennings, Mr. Candy's assistant, on his way out. They start talking and Franklin discovers that Ezra is currently doing an extensive study on memory and memory loss. Ezra believes that he has figured out a way to discover what happened. By listening to Mr. Candy's ramblings during his illness, he deduces that Candy had slipped opium into Franklin's drink. Using the new theory of stat- dependent memory, Ezra believes that Franklin might be able to remember or repeat the actions of what happened the night of the birthday with the use of opium and under the correct conditions. Franklin immediately agrees to take part in the experiment. So ends the fourth period.
The fifth period is taken from Ezra's medical journal. It chronicles the experiment done to determine what Franklin did the night of Rachel's birthday. Franklin once again tries to quit smoking and the Verinder house is furnished to look almost exactly the same as it did the year before. Ezra ends up writing Rachel a letter, letting her know of the
activities going on in her old house, and she begs to be allowed to witness the experiment. She wants to see Franklin's name cleared almost as much as he does. After Franklin is in an agitated state, he is given the opium and sent to bed. Rachel hides in her old room with a crystal representing the Moonstone in the cabinet. At first, Franklin does not respond to the effects of the opium, however, a little after midnight, he gets out of his bed and starts muttering about how worried he is about the Moonstone being stolen and how he wants to hide it somewhere. He leaves his room, goes into Rachel's, and takes the fake diamond from its hiding place. Unfortunately, Ezra gave Franklin just a little too much opium and the sedative effects kicked in before Franklin could finish his drug-induced task. He passes out on Rachel's couch. Ezra does not see the experiment as a total failure, since Franklin did indeed repeat his actions from the birthday and therefore clears his name. However, there was still no answer as to who put the Moonstone in Mr. Luker's possession. Rachel and Franklin make up and return to London to try to determine who stole the Moonstone as said person attempts to retrieve it from the bank. So ends the fifth period.
Franklin resumes narrating the next period. He is reunited with Sergeant Cuff, who comes out of retirement to finish the case. They and some of Sergeant Cuff's men watch the bank for Septimus Luker. When they see him, he passes something to a swarthy man who looks like he could be a sailor. A boy in Sergeant Cuff's employment, nicknamed Gooseberry, follows him the entire day and notices that another man, who looks like a mechanic, is following him as well. Gooseberry continues to follow the sailor to an inn where he stays for the night. All is quiet. The next day he reports back to Franklin and Sergeant Cuff and tells them the sailor's whereabouts. They go to the inn, only to find that the sailor has been locked in his room since that night and hasn't come down, even though he was only booked for one night at the inn. With the help of the inn's owner, they break down the door to find the sailor on the bed with a pillow covering his face...dead. A small jewelry box stuffed with cotton is sitting empty on the bedside table, and everyone is sure that it once contained the Moonstone. Sergeant Cuff inspects the body and finds out that the man is wearing a disguise. Upon removing it, they are confronted with the face of Godfrey Ablewhite. He had been the thief of the Moonstone.
The final part of the book consists of Sergeant Cuff's outline of the case and Godfrey's motives for stealing the Moonstone. The empty box in Godfrey's room had, in fact, contained the Moonstone, according to Septimus Luker. In addition, the Indians had smothered him and stolen the diamond. Godfrey's motive for stealing the Moonstone was the acquisition of twenty thousand pounds that was to be paid to a young gentleman, a minor at the time. Godfrey was named a trustee of the young man's fortune, but he squandered the money he was entrusted with. In order to get it back in time to give it to the young man, he tried to marry Rachel the first time. In light of that failure, he took the Moonstone from the opium-hazed Mr. Franklin and entrusted it to Mr. Luker. There is also a letter from Mr. Candy to Franklin informing him of the death of Ezra Jennings, (who was ill with an unspecified ailment) as well as a snippet from Gabriel Betteredge about Franklin and Rachel's wedding. The final pages of the book are a letter from Mr. Murthwaite
telling of a ceremony he witnessed upon his return to India. The Moonstone had found its way back to its rightful place in the forehead of the moon god statue.