Most of the key events in the movie are based on historical events or reports about the life of Saint Joseph of Cupertino. Born Giuseppe Desa, he was said to have been remarkably unclever, but was recorded by many witnesses during his life as prone to miraculous levitation and intense ecstasies.
The film begins with Giuseppe (Maximilian Schell) spending his final days at home with his mother (Lea Padovani). Due to his slow wits, she has kept him in school despite his being a grown man, older than the other students. He is seen bearing patiently and good-heartedly the ridicule of his fellow villagers, and enduring failed attempts at work as a laborer. At the insistence of his mother, who saw no other viable alternative, he enters a Franciscanfriary through the influence of his uncle Father Giovanni (Harold Goldblatt), an authority in the religious order. Trouble follows Giuseppe wherever he goes, including the friary, because he is slow. Eventually, his good heart is noticed by the visiting Bishop Durso (Akim Tamiroff), a man of similar peasant background who then orders the friars train Giuseppe for the priesthood.
Despite Giuseppe's incapacity for the necessary academic studies, and preference for tending the sheep and other animals in the friary’s stable, he is ordained a priest. Although he learns little from the tutoring of other friars like Brother Orlando (Giulio Bosetti), Giuseppe passes the necessary examinations for the priesthood through a series of unlikely or possibly miraculous events. Soon after, when Giuseppe is seen levitating in ecstatic prayer to the Blessed Virgin Mary and during the conventual Mass, one of the superiors in the community, Father Raspi (Ricardo Montalbán), accuses Giuseppe of suffering from demonic possession. Giuseppe is thus chained to the ground by his brother friars then subjected to an exorcism, but his levitations continue, persuading everyone – including his former critic Father Raspi – of the divine origins of his powers.
