Gothic horror revolves around a Roman Catholic priest and a nun in her novitiate as they uncover an unholy secret in Romania. In 1952 two nuns from the Saint Cartha's monastery are attacked by an unseen evil 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. After her body is discovered, the Vatican summons Father Burke to Rome, where they ask him to travel there with Sister Irene and carry out the investigation.
