When Coyotito, a very young child, is stung by a scorpion, Kino, his father, must find a way to pay the town doctor to treat him. The doctor denies Kino out of racism, which enrages him. Shortly thereafter, Kino discovers an enormous, lucid pearl which he is ready to sell to pay the doctor. Everyone calls it "the Pearl of the World," and many people begin to covet it. That very night Kino is attacked in his own home. Determined to get rid of the pearl, the following morning he takes it to the "pearl buyers auction" in town; however, the "auction" is actually a corrupt sham and always has been. The "buyers" normally pretend to auction each pearl and pretend bid against each other, but in reality they are all paid a salary by a single man, they all turn the pearls over to him and he resells them outside the village, thus cheating the locals. The corrupt pearl buyers try to convince Kino that the pearl is the equivalent of "fools gold" and they refuse to pay any more than incredibly low amounts of money. Kino decides to go over the mountains to the capital to find a better price. Juana, Kino's wife, sees that the pearl brings darkness and greed, and sneaks out of the house late at night to throw it back into the ocean. When Kino catches her, he furiously attacks her and leaves her on the beach.
While returning to his hut with the pearl, Kino is attacked by an unknown man whom he stabs and kills. Kino thinks the man has taken the pearl, but Juana shows him that she has it in her possession. When they go back to their hut, they find it has been set on fire. The family's canoe had also been ruined, an offense that enraged Kino. Kino and Juana then spend the day hiding in the hut of Kino's brother Juan Tomás and his wife, gathering provisions for their trip to the capital city. Kino, Juana, and Coyotito leave in the dark of the night. After a brief rest on their journey in the morning, Kino spots trackers he believes are following them. Well aware they will be unable to hide from the trackers, they begin hiking into the mountains. They find a cave near a natural water hole where the exhausted family hides and waits for the trackers to catch up to them. Kino realizes they must get rid of the trackers if they are to survive the trip to the capital. As he prepares to attack, the men hear a cry like a baby's, though they decide it's more like a coyote with a litter. One of the men fires his rifle in the direction of the crying, where Juana and Coyotito lie. Kino kills all three of the trackers. Realizing that something is wrong, he climbs back up to the cave to discover that Coyotito has been shot in the head when the tracker fired. In the morning, Kino and Juana return to La Paz with Coyotito's dead body wrapped in a sling. No longer wanting the pearl, Kino throws the pearl back into the ocean.