Antonio learns his mother's brother, Uncle Lucas, has been cursed by witches—the daughters of Tenorio. Apparently, it's so bad he's now dying.
Ultima's got plans to go to Lucas to cure him, and she'll take Antonio with her, which sounds like maybe not the best thing to take a kid to.
Off they go… into the lion's den. Ultima confronts Tenorio in his bar as Antonio looks on (again: bad scene for a kiddo, right?). She states plainly, "I am a curandera […] and I have come to lift a curse. It is your daughters who do evil that are the brujas"(10.37-39).
At Lucas's, Ultima gets going on what you might call an exorcism, but it's nothing like the movies.
During the exorcism, the evil is taken from Lucas and transferred into Antonio, which is all kinds of bad.
In the end, there is a lot of vomiting (okay so maybe it is like the movies) from both little Antonio and Lucas. In fact, when it comes to Lucas, "Green bile poured from his mouth, and finally he vomited a huge ball of hair" (10.630-631). Um, gross?
The curse is lifted, and Lucas heals. Yay!
Ultima and Antonio return home, so we guess all's well that ends well.