Essentially, Steinbeck has Kino and Juana return to La Paz in order to
b. perform a symbolic act.
Kino and Juana return to La Paz to throw the great pearl away into the sea. The pearl, which was to have been the answer to all their prayers, has brought nothing but disaster. The riches which Kino had envisioned attaining by selling the pearl have not materialized, and instead, he and Juana have lost everything of value to them, including the most valuable thing of all, their son Coyotito. Before he throws the pearl away, Kino looks at it closely and sees that
"it (is) gray and ulcerous...evil faces (peer) from it into his eyes...and in the surface of the pearl he (sees) Coyotito lying in the little cave with the top of his head shot away...and the pearl (is) ugly, it (is) gray, like a malignant growth...and Kino hear(s) the music of the pearl, distorted and insane".
Kino flings the pearl "with all his might" into the water, and as it settles to the bottom of the sea, and "the music of the pearl drift(s) to a whisper and disappear(s)". It had brought out nothing but the darkest evil in all those who coveted it, and now that it is gone, that cloud has been lifted, the evil vanished.
Although the ritual which Kino and Juana perform in throwing the pearl into the sea is symbolic, the author gives us a sense that the change for which the action stands has already taken place in their own lives. The two return to their village walking side by side, not "in single file, Kino ahead and Juana behind, as usual". They are introspective, and have begun to throw aside traditional values and customs in favor of ones they have chosen themselves, ones based on love. The author does not say exactly what will happen to Kino and Juana, or what they will do once they resume their lives in the village. He only lets us see that their lives have changed, as exmplified by their symbolic act of throwing the great pearl back into the sea (Chapter 6).