Kino, the novella's protagonist, is a young Mexican-Indian pearl diver married to Juana; they have a baby named Coyotito. Their lives seem rather peaceful, but their tranquility is threatened when a scorpion bites Coyotito. Juana tells Kino to go to town and get the doctor, but Kino and their neighbors tell Juana that the doctor will never come to where they live, so Juana decides to take matters into her own hands and sets off with Coyotito to the doctor. Kino accompanies Juana, and many members of the village follow them to see what will happen. At the doctor's house, the doctor's servant tells Kino and Juana that the doctor is not at home — in truth, the doctor is home but will not help Coyotito because Kino cannot pay the doctor as much as the doctor wants, but also because the doctor is prejudiced against Kino's race.
Kino goes to work diving in the Gulf for oysters from his canoe; Juana tends to Coyotito in the canoe by applying brown seaweed to his shoulder, which is swollen from the scorpion's bite. As Kino is collecting oysters on the ocean bottom, he spots a larger-than-usual oyster, collects it, and returns to the canoe. Kino does not want to open the oyster immediately, but Juana prompts him to open the oyster; when he does, he finds a pearl the size of a sea gull's egg. Juana gazes at the immense pearl; she then goes to check on Coyotito and discovers that Coyotito's shoulder is no longer swollen. Kino is immensely happy about both the pearl and Coyotito and yells loudly enough that he attracts the attention of the other oyster divers, who race toward his canoe.
