The story is a simple tale about Kino, an Indian pearl diver. In the beginning, Kino lives a simple life, loves his family, and enjoys complete contentment; but the story tells about how his discovery of the most wonderful pearl in the world shatters his happiness. In the first chapter, Kino's calm life is interrupted when a scorpion stings his infant son, Coyotito. Kino's wife, Juana, insists that they take the baby to the doctor in town. Cruelly, the doctor refuses to treat the infant, for Kino does not have the money to pay his fee. In anger, Kino strikes out at the doctor and all he stands for when he bangs and injures his hand against the doctor's gate.

Kino returns to the beach with his family. He, along with Juana and Coyotito, rows out to an oyster bed, where he begins his work. After gathering several small oysters, he spies a giant one that reveals it has a pearl inside. He quickly picks it up and comes to the surface. Back in the canoe, he opens the large oyster and discovers the most wonderful pearl in the world. News of Kino's treasure travels rapidly through the town. Everyone is envious of Kino's pearl, and many think of ways to acquire some of Kino's future riches. During the night, someone comes into Kino's hut, searching for the pearl. The "dark force" injures Kino before he flees. Juana begs Kino to get rid of the pearl, which seems to be causing evil things to happen to them.

The next day, Kino dressed in his best rags, goes to town to sell his treasure to the pearl buyers. Working in a unified manner, they all tell Kino that his pearl is worthless and offer him a really low price. Kino refuses to sell the pearl and states that he will take it to the capital, where he feels certain he will get a just and higher price. That night, Kino is again attacked in his hut as the "dark force" seeks to steal the pearl, which Kino has carefully hidden. This time Juana takes matters into her own hands. She unearths the pearl and takes it to the beach to throw it back into the gulf. Kino stops her from her action and saves the pearl. He is so enraged at his wife's behavior that he knocks her down and kicks her. Obviously, the pearl is changing Kino.

On the way back to his hut, Kino is again attacked. This time, he stabs and kills his assailant. As a result, he and Juana are forced to quickly flee from La Paz. Before leaving, they discover their canoe has been destroyed and their hut has been burned. Kino now feels like a pursued animal, but he still refuses to part with the pearl. He, Juana, and Coyotito move through the arid desert, being closely followed by professional trackers who want the pearl. When they reach the mountains, Kino hides Juana and the baby in a cave. He goes to attack the trackers. He stabs and kills the first two of them; when the third one tries to escape, Kino takes their rifle and fires shots at him. One of the bullets enters the cave and kills Coyotito.

 

Juana and Kino return to their village to bury their child. The pearl no longer has a value to them, for all their dreams and happiness have vanished. As a result, they walk to the beach and toss the pearl back into the gulf. They watch silently as it sinks into the dark waters.