The first turning point is the finding of the pearl, and the subsequent invigoration in Kinos' mind of a different life for his family. He predicts,
"My son will read and open the books, and my son will write and will know writing. And my son will make numbers, and these things will make us free because he will know - he will know and through him we will know...This is what the pearl will do."
The next turning point is the change from promise to poison. The discovery has ruined their lives, "It will destroy us all," Juana cried. "Even our son."
Another revolution comes when the problem of the pearl results in Kino's murder of a man he suspects of trying to steal his treasure. Still,
"Kino thrust the pearl back into his clothing, and the music of the pearl had become sinister in his ears and it was interwoven with the music of evil."
Kino is under the spell of the pearl and it will take the death of his son, Coyotito, to return the dial to morality. Finally, he clearly sees the true nature of the pearl:
And the pearl was ugly; it was gray, like a malignant growth. And Kino heard the music of the pearl, distorted and insane...And Kino drew back his arm and flung the pearl with all his might....They saw the little splash in the distance..And the music of the pearl drifted to a whisper and disappeared.