At the beginning of chapter three, Kino and Juana have just found the largest pearl anyone in their village and nearby town could ever dream of. Before they are even able to return from the nearby ocean to their tiny brush house both their village and the joining town are ablaze with the news of their discovery of their massive pearl. When the news spread to the doctor who had refused to treat Coyotito's ailment he is indignant and announces to anyone who will listen that Kino's child is his patient who he is treating for a scorpion sting. It's not just the doctor, however, who is made greedy by Kino's good fortune. Shopkeepers wonder if he will come and buy clothes for his family, the beggars in front of the church are pleased because they know that "here is no alms giver in the world like a poor man who is suddenly lucky."

From the moment Kino's pearl it feeds the darker desires of both the wealthy towns people, and the poor indigenous community that live in Kino's village. Kino and Juana, however, are oblivious to the fact that the communities around them have been rendered toxic by their luck. The little family is simply pleased and excited about their own good fortune, and in their innocence they believe that everyone around them is pleased by their serendipitous discovery.

A neighbor asks Kino what he will do now that he is wealthy man. Kino can think only of a long time dream: to marry Juana in the town's church. Something he had never before thought possible, because he did not have enough money to pay for the simple ceremony. In the pearl he envisioned the family at the wedding dressed entirely in new clothes, and something they had never had before: shoes. The question as to what Kino will do with his new wealth spawns a lot of possibilities for him, for example he thinks he might buy a harpoon, and then a riffle, and then the impossible: he imagined that his son might go to school, and said as much to the villagers gathered around his family. These simple people are shocked by the notion that child from their very own village might someday attend school.

However, Juana and Kino continue on with their normal lives. The very night they find the pearl Juana interrupts the village's excitement by returning to her normal duties as wife and mother. As Juana builds her fire, and the village settles back into feigned normality the local priest comes to visit. Normally, the priest treats the indigenous population with contempt, but Kino is of sudden interest to him. The village greets their visitor with reverence despite his normal apathy towards them. The priest asks to see Kino's pearl, and tells him slyly that he hopes Kino and his wife will remember that God had blessed them with its discovery, and that they should bless God in return. Kino sees the priest's greed, and the pressure he is putting on him to donate to the church, and feels uneasy.

The priest leaves without explicitly asking for anything, but more unusual visitors from town soon follow him. The doctor who had refused to treat Coyotito quickly follows the holy man. Kino regards him with suspicion, and tells him that Coyotito is improving and no longer requires his assistance. However, the doctor is manipulative. He tells the baby's parents the scorpion stings can often appear to be improving externally, while they kill internally. Out of fear Juana and Kino allow the doctor to inspect their child, he declares that the venom is working internally, and gives the baby a white powder. He says that he thinks he has intervened in time, but will come back in an hour to check on Coyotito. While he is away the infant becomes desperately ill. The physician returns, and like magic, heals the ailing baby. Juana is grateful, but Kino is suspicious. The doctor asks when they can pay him, and Kino tells him that they will pay when he has sold he pearl, which the doctor pretends not to know about.

During the night Kino descends into paranoia and distrust. He hears a noise outside his hut, and goes to attack the intruder, but falls on his head injuring himself. Juana declares that the pearl is a "think of evil" that will destroy the family, but Kino reassures her that when he sells the pearl in the morning the evil will be gone, and only the blessings will remain.

As Chapter four opens word has spread that Kino will be selling his pearl. Everyone in the town and surrounding villages stop their normal daily activities to see how much the pearl will sell for. Kino's brother Juan Tomás follows Kino and Juana as they make their way towards town, and expresses his concern that Kino might be taken advantage of because he doesn't know the true value of his pearl. Kino agrees with his brother's assessment, but also points out that there is no real way to find out what it is worth.

When Keno arrives in town there are throngs of people gathered around the pearl buyers. The first man to approach him says that the pearl is not of any real value because of its abnormal size, and because its only value is as a curiosity, only offers Kino one thousand pesos. Kino is angered by the man's low offer, and adamantly tells the man that his pearl is worth at least fifty times what he offered. Kino's neighbors, however, think that he might be foolish for not accepting an offer of so much money. After Kino refuses the first offer, another man places a five hundred pesos bid on the pearl. Incensed Kino removes the pearl from local consideration, and announces that he will go to the capital to sell it. This sparks a fever among the pearl buyers, who bid the rarity up to fifteen hundred pesos, but Kino is unimpressed and goes home with the pearl.

When he arrives home he buries the pearl in a hole under his sleeping mat. Kino's brother Juan visits, and attempts to talk him out of going to the capital because he believes it to be dangerous. Kino explains that he is willing to risk the trip because he is determined to secure a better future for his family. Kino and Juana sit vigil over the pearl all night. Sometime towards morning Kino sense an evil presence. He attempts to attack the intruder with his knife, but the strange man assaults him first. Kino is badly hurt in the scuffle, and by the time it is over he is only semi-conscious. Juana dresses his wounds, and again begs him to discard the pearl. He assures that tomorrow they will go to the capital via canoe and rid themselves of their burden.