Sister Leopolda is a bullying nun with a strong sense of Satan's presence. Marie gets into conflict with her during Sunday School and decides she wants to win against her, so she becomes a novice at the Sacred Heart convent where Sister Leopolda lives. She decides that if she can get to heaven first, she can keep Sister Leopolda out.
At the convent, the conflict between Sister Leopolda and Marie escalates. When Marie is retrieving a cup from under the stove, Sister Leopolda pours boiling water on her to free her from Satan. Sister Leopolda tries to rub balm on the burns, but Marie fights her and tries to push her in the oven. Sister Leopolda then stabs Marie with a fork and knocks her unconscious with a poker as the two vie for dominance.
Marie wins this battle. To cover up her abuse, Sister Leopolda passes off the fork stab wound in Marie's hand as a miraculous appearance of stigmata from heaven. The nuns are awed and view Marie as a saintly or godlike figure.
However, though Marie wins the fight to dominate her rival, she learns to feel pity for Sister Leopolda.