In the North American Pontifical College, in Rome, Father Maurice (Walther Matthau) is in deep turmoil because of Patricia (Stefania Sandrelli), a woman who loves him and expects him to make up his mind and clear out his position towards her. While he is trying to do so, he is summoned by a novice for an emergency. The emergency turns out to be a fat woman possessed by a demon. Father Maurice performs the rite of exorcism and expels the demon from the woman. The demon (Roberto Benigni), a little escaped devil named Giuditta, having nowhere else to go, starts following Father Maurice everywhere and often indulges in mischief getting Maurice in trouble. In one instance Giuditta replaces a sick Father Maurice in Mass, turning the solemn ceremony in a beauty parade. Maurice tries to get rid of Giuditta in several failed efforts. Showing signs of exhaustion, his peers advise him to take a vacation. Eventually another agent "from where Giuditta came from" appears as Nina (Nicoletta Braschi) and manages to attract Giuditta who finally leaves Maurice and follows her "elsewhere".