The conflict between good and evil in the novel is characterized through the relationship between Ultima and Tenorio. From the start, Ultima is described as the moral compass for the novel, protecting her community from the curses of evil witches. Tenorio, on the other hand, takes his place as Ultima’s arch-nemesis who shares his wicked daughters’ penchant for cruelty and evil. The battle between these two characters perpetuates the majority of the plot in the novel and, although both characters die at the end, Ultima’s goodness and Tenorio’s evilness are maintained.
However, as Antonio himself discovers, good and evil are not so easy to distinguish. Although Ultima performs many good deeds, she kills two of Tenorio’s daughters with her counter curse, using pagan powers that go against Catholic beliefs. The incident with the holy cross in Chapter 12 brings to light additional questions about Ultima’s “goodness” in the eyes of the church. Tenorio’s true evil is equally difficult to determine; his attempts to murder Ultima are only the result of his wish to avenge his daughter’s death. In some novels, a mourning father who seeks revenge would be the hero, rather than the antagonist. In both cases, neither character is easy to define as wholly good or wholly evil.
Near the end of the novel, Anaya explains that the goodness of a person is determined solely by his or her actions. Within this framework, Ultima still possesses much more "good" in her nature than Tenorio does. However, it is clear that good and evil cannot be distinguished in a clear-cut way, and this is one of the more important lessons that Antonio learns about life.