In Louise Erdrich's novel, Love Medicine, Sister Leopolda and Marie have an unhealthy relationship: Sister Leopolda sees Marie as a soul the Devil craves, and she is physically and emotionally abusive toward Marie based on this assumption. Marie, who also believes the Devil wants her, as Sister clearly tells her, believes the only way to be victorious over Sister Leopolda is to beat her to Heaven.
As the story begins, Marie is in Sister's class. There is an incident there (Marie believes the Dark One is in the closet, and smiles); somehow Sister knows, and Marie ends up locked in the closet. This is when Marie decides how best to beat Sister. She and Sister have a discussion, and literally, Sister tells Marie that she has two choices: she can marry an Indian, give birth to his "brats" and "die like a dog," or she can "give herself to God."
However, in a more subversive way (based upon how Marie reacts to her words), Sister tells Marie she can have the Devil or love.
'He wants you,' she said. 'That's the difference. I give you love.'
Marie thinks to herself:
Love. The black hook. The spear singing through the mind. I saw that she had traced the Dark One to my heart and flushed him out into the open. So now my heart was an empty nest where she could lurk...Well, I was weak.
Marie stays at the convent for a several years. The battle between Sister and Marie rages. Eventually, however, Marie is able to place doubt in Sister's mind and heart. Sister is a crusader against "the Dark One." She fights the battle everyday, though the other sisters have long since doing so.
At one point, Sister pours boiling water from the stove top onto Marie's back to drive the Devil out of her. Marie does not utter a sound, and strangely, when it is done, Marie tells Sister how hard she prayed, and Sister responds, saying, "My dear one, I know." Sister, with a twisted sense of "love," puts a salve on the girl's back, but Marie has finally had enough. She knows she must leave before she is completely broken. She yells at Sister,
'He was always in you,' I said. 'Even more than in me. He wanted you even more. And now he's got you. Get thee behind me!'
...[Sister Leopolda] was pretending nothing happened. But for the first time I had gotten through some chink she'd left in her darkness. Touched some doubt.
It is in this way that Marie plants a seed of doubt in Sister. Sister pushes Marie on, insisting that she help while Sister takes bread out of the oven. Enraged, Marie tries to shove Sister into the oven. Sister is saved at the last minute by the fork and poker she holds. With these, she stabs Marie in the hand, and knocks her in the head, into unconsciousness.
When Marie awakes, Sister has told the other nuns that Marie has the sign of the stigmata (wound of Christ at his crucifixion) on her, and all are surrounding Marie in prayer. Marie realizes that Sister has told the story to protect herself.
Marie knows she has won. And she is ready to make Sister pay. However, she looks at the beaten nun, aware of her personal "wrongness," "kneeling within the shambles of her love." Marie knows that there will be no girls abused by Sister Leopolda from this point on. Rather than collecting the debt she had planned to acquire for years of abuse, Marie can only see Sister with pity in her heart, and know now that she can leave.