Ecclitico: Ugo Benelli
Scholar 1: Peter O'Leary
Scholar 2: Gerard Delrez
Scholar 3: Graham Trew
Scholar 4: Greville O'Brien
Buonafede: Gianni Socci
Ernesto: Alan Watt
Cecco: Dennis O'Neill
Clarice: Elaine Linstedt
Flaminia: Helen Dixon
Lisetta: Emily Hastings
A terrace in the house of the bogus astronomer Ecclitico; an observatory tower with a telescope. A starlit night, with full moon
Ecclitico and his four students sing a hymn to the Moon, and Ecclitico boasts of how he can dupe the foolish – such as Buonafede, who now appears. Buonafede does not have a clue what the Moon is. Ecclitico explains to him that through his powerful telescope he will be able to see the Moon's transparent surface all the way through the houses and able to spy on ladies as they undress before going to bed. Buonafede then attempts to view the Moon through Ecclitico's telescope while Ecclitico's servants move caricatures in front of the telescope's lens. The trick works: Buonafede describes what he thinks he has seen: a very beautiful young girl caressing an old man, a husband ready to punish his wife for her infidelity, and a man who completely dominates his female lover. He rewards Ecclitico with some coins and leaves.
Alone, Ecclitico muses that it is not the old man's money he wants, but to wed his daughter Clarice. Ernesto, a nobleman who is in love with Clarice's sister Flaminia, and his servant Cecco (in love with Buonafede's servant, Lisetta) now join Ecclitico. Buonafede intends to marry the sisters off to rich suitors.
Ecclitico assures Ernesto and Cecco that with a little money all their difficulties will be solved. In a more serious aria ("Begli occhi vezzosi"), Ernesto sings of Flaminia's eyes and awaits impatiently the moment in which the two of them will spend their lives together. Cecco, for his part, is convinced that everyone's playing games and insistently points out the comic side of life.
A room in Buonafede's house
The sisters Clarice and Flaminia dream of escaping their tyrannical father. In a long aria, Flaminia recognises that even if reason is to dominate the soul, when love intervenes it takes control of everything. Buonafede mocks Clarice's stubbornness but she answers back, threatening him that she will find a husband for herself if he is not capable of providing one for her. The two sisters are clearly differentiated: Clarice is down to earth and her arias are full of determined pragmatism. Buonafede invites Lisetta (his daughters' maid) to share the wonders he has seen through the telescope, in an attempt to win her over. Interested in his money, she reassures him of her love for him, her fidelity and her virtues, none of which is true. Ecclitico arrives and tells Buonafede that the Emperor of the Moon has invited him to his court. By drinking an elixir he will be transported to the Moon. Buonafede is tempted to travel with him and, therefore, asks for some of the liquor. Ecclitico agrees and, pretending to drink half of it, gives the rest to Buonafede who drinks it, falls asleep, and dreams of flying to the Moon. Clarice and Lisetta believe at first that he is dead, then console themselves with the inheritance they will be getting.
Ecclitico's garden, decorated so as to convince Buonafede that he is on the Moon
Ecclitico and Ernesto discuss the progress of their plot, and when Buonafede awakens he is convinced he is on the Moon. He is entertained by a ballet and clothed in elegant gowns. Ecclitico tells him that he will be joined by his daughters and servant. According to lunar custom the women will be meek. Cecco appears disguised as the Emperor of the Moon, with Ernesto as the star Hesperus. Buonafede, delighted with life on the Moon, is entertained by another ballet. When Lisetta enters, Buonafede tries to court her, but Cecco asks her to become Empress of the Moon. Lisetta, not fully aware of the plot, is at first puzzled. The two daughters arrive and pay homage to the Emperor in a nonsense ceremony. Flaminia goes off with Ernesto and Clarice with Ecclitico, while Cecco prepares to crown Lisetta as Empress. In the confusion of the masquerade, Buonafede is tricked into consenting to the three marriages, only realising that he has been duped when it is too late.
A room in Ecclitico's house
The conspirators, back in normal dress, have locked Buonafede in his own house – the price of his freedom will be forgiveness for his daughters and their dowries. At last he yields.
A starlit night with a full moon
Clarice and Ecclitico sing of their love. Buonafede repents of his previous strictness and there is general rejoicing and celebration.