In "Saint Marie," Erdrich explores such themes as racism and prejudice. For instance, she examines the various ways Sister Leopolda discriminates against Native Americans, while pushing her audience to understand why it is important to question such behavior. Faced with an ambitious Marie who seeks sainthood and to "inherit [her] keys," Sister Leopolda senses implicit animosity from forces outside her order, both literal and metaphorical. Leopolda's behavior indicates how racism can stem from fear of displacement.
Yet despite their different ages and backgrounds, Marie and Leopolda understand one another. Each recognizes the soul of the other, and each knows the extent to which the other will go to manipulate the power granted through institutionalized religion.
The potential to transcend cultural differences is within reach. That Marie and Leopolda are not able to do so suggests that religious and cultural barriers can be very difficult to break.