It's 1477 in the province of Julich-Berg of the Holy Roman Empire, where a group of nuns and monks have an accord with the Duke of the province to protect the lands against the beings of Hell. But Duke's younger nephew wants to take his place, so he tries to use the knowledge of the abbey to summon Astaroth, a powerful demon. When the ritual fails and a lesser demon is summoned in its place, Sister Irene is commanded to kill it. She doesn't have the heart to do it, so instead, she decides to hide and protect the weak demon.
The longer the demon remains on earth and learns the ways of humans, more complicated life becomes for Sister Irene, as she is unable to resolve the conflict between growing maternal instincts and the sense of duty to her calling. But as she is denying the benevolent demon a bond that would keep him corporeal, the demon's body keeps disappearing.
Will Sister Irene let her sacred duty or call of motherhood prevail, and will the demon be able to survive amidst growing tensions, as his body slowly disintegrates due to the lack of connection to the human world?
