Coyotito gets stung by a scorpion early in the morning while laying in his bed. His mother, Juana, gets very scared and attempts to suck the poison out of Coyotito's arm. Kino attempts to save Coyotito by killing the scorpion, but it was too late, he was already infected with the poison.
Kino begs the doctor to treat Coyotito. He offers to pay for it with a couple small pearls he has, but a rich doctor almost never tends to a poor family. The doctor refuses to treat Coyotito.
Kino and Juana go out in Kino's canoe to search for a large enough pearl to pay for Coyotito's treatment. Juana prays as Kino dives into the water. Kino discovers a large oyster and brings it to the surface with hope it contains a large pearl. He opens it and finds the largest pearl he's ever seen. Kino and Juana are overwhelmed with joy.
When the doctor hears word of the newly discovered pearl, he comes back to Kino's village. He wants part of the wealth that is going to come from the pearl, so he offers his treatment to Coyotito. Juana is suspicious of the doctor as she notices he only offers treatment when there is potentially a lot of money involved. However, Kino lets the doctor in.
Juana expresses her concerns to Kino about the doctor. Kino is also nervous of the pearl being stolen. He decides to bury the pearl when the doctor offers to protect it for him.
In the middle of the night, someone attempts to steal the pearl from the place where Kino hid it. Luckily Kino wakes up and it able to scare the burglar off with a knife.