A pearl diver's baby gets stung by a scorpion, but he can't pay the town doctor. Luckily, he discovers the greatest pearl in the world. He lets on, and soon he's being attacked in his own home. The sensible thing is to head to town and sell it, right?
In the brilliantly realized setting, class struggle is ancillary (exploited by those who understand it). When scare tactics fail them, the rich and hopeful-rich turn to violence.
Genuinely surprised at the results, Juanita thinks the pearl a demon and Kino blames the rich. Both are victims of naive, backwards thinking. The only difference between them and the fat, pitiless doctor is savvy.
Steinbeck again proves himself a master of English prose and storytelling.