Ademar, the son of a Sicilian prostitute who pretends to be an oriental prince, and Ezzelino, a Roman friar who abandoned his vows and pretends to be a great luminary, form a kind of 'criminal association' selling the poor people false remedies of eternal youth, beauty and so on.
With the approach of the year One Thousand and the legend of the 'Thousand and No More Thousand' and 'finismundi', the masses abandon the purchase of Ademar and Ezzelino's potions and devote themselves to penance and fasting in view of the Divine Judgement. So the business of the two languishes, and one night Ezzelino thinks well of abandoning his companion by stealing a cart, shoes and goat.
Some time passes, and Ademar happens upon a small village where Ezzelino pretends to be a cripple in order to collect alms. Ademar, in order to unmask him and take his revenge, forces him to walk, and the people immediately cry out for a miracle and identify Ademar with the Man with the White Cloak announced in the prophecy of the Holy Monk Nicosia, who will have to make a cripple walk, redeem a prostitute, resurrect a dead man and turn the water in a fountain red before setting himself on fire to open the gates of Paradise for mankind.
Ademar, with the interested help of Ezzelino, seizes the opportunity and immediately 'redeems' the prostitute Belcore, imprisoned by the penitents in a cage. He then proceeds to resurrect the dead man. Ezzelino pretends to die but Ademar cannot prevent him from being taken to the cemetery, where he has strange and comical adventures. The following day, however, Ademar resurrects him, and together the two swindlers start selling scapulars, promising eternal salvation in exchange for the renunciation of all possessions. Archiepiscop Lothair also arrives, who also believes the prophecy of Saint Nicosia.
Meanwhile, the vicissitudes of Ezzelino and the virginal Peronella and of Ademar and Belcore intertwine. Ezzelino, realising that by now Ademar is convinced he is a true holy man, deceptively completes the transmutation of the fountain's water into red: or at least he believes he did it, while it was the Archiepiscop with the complicity of the petty thief Folchetto. However, while convinced Ademar is on his way to the stake, Ezzelino discovers that he did not turn the fountain water red, and convinces himself of the imminent end of the world by handing over all the goods they stole to Lothair in exchange for a scapular.
Ademar is made aware of Ezzelino da Belcore's deception, and the two friends confront each other, but will return together to take back the riches in Lothair's hands. Lothair, meanwhile, urges the people to go to Rome to solicit his proclamation to the Papacy, and claims that the riches extorted from the people are the property of St. Peter. Therefore Ezzelino disguises himself as St. Peter and claims the sack of riches, and Lothair must surrender it. At this point, Ademar disguises himself as Jesus Christ, and Ezzelino-Pietro surrenders the sack to him, in an amusing sequence of changing hands of the sack.
Finally, the people discover that the end of the world has not happened, and Ademar and Ezzelino go back to selling potions to the poor people.