A child is witness to an assault on a monk by the gang of Lorenzo the Fifth. The monk escapes and takes refuge in the estate of Doña Carlota, a countess who lives with her son Juan and daughter Beatriz. Basilisa, the maid, conjures the devil to free her son from an irreversible illness, but to do so the evil must be transmitted to an innocent soul, and for that she chooses Beatriz. The child begins to be the victim of a possession, for which everyone blames the monk.