The Nun

In 1952 Romania, two Roman Catholic nuns living at the Saint Cartha's monastery are attacked by an unseen force when they enter a tunnel to retrieve an ancient Christian relic. The surviving nun, Sister Victoria, flees from the attacker, a demon appearing as a nun, and hangs herself. Her body is discovered by Frenchie, a villager who transports supplies to the nuns.

The Vatican learns of the incident and summons Father Burke to Rome, where they ask him to travel with Sister Irene, a nun in her novitiate, to Romania in order to investigate the situation. While Sr. Irene is teaching children the relationship between religion and science in a school, her Mother Superior interrupts her and informs her that Burke has arrived in order to request Irene's accompaniment in his trip to Romania.