A Mother superior in a 17th-century convent finds herself possessed by the Devil in this Polish drama set in a convent of Ursuline nuns. Several attempts are made to exorcise the demon. While four priests attempt to banish the spirit, two more are burned at the stake for impregnating her. All but one of the other nuns allow Satan's minions to enter their bodies. An extremely devout priest uses every power at his disposal to exorcise them. But even self-flagellation cannot stop them. In desperation, the priest consults an aged rabbi who suggests that the "demons" are really manifestations of human nature. The priest then finds himself becoming possessed by the Mother Superior. Suddenly he desires her body and soul. To prove his desire, he murders two stable grooms. He then encounters the one unpossessed nun who has just spent a night of lovemaking with an aristocrat who has since tossed her out. She is terribly upset and the priest advises her to go back to the convent and tell the Mother Superior of the lecherous man's misdeeds.