It is night time, and a young girl is swept away by the power of her imagination into a world where nothing is as it first appears…

Here she finds Tamino, a handsome prince who is also lost in this strange land, and is being pursued by a monstrous serpent. Three mysterious women appear, who are servants of the Queen of the Night, and slay the monster. Afterwards, they give Tamino a portrait of the Queen’s daughter, Pamina, and he falls instantly in love, vowing to rescue her from the evil Sarastro, Priest of the Sun, in whose faraway Temple she has been imprisoned. The three women give Tamino a magic flute to help in his quest and with the aid of a bird-catcher, Papageno, Tamino journeys to Sarastro’s temple and meets Pamina for the first time.

Despina persuades Fiordiligi and Dorabella to see the strangers once more. Admitting that there is an attraction, they speculate over which of the new men they would choose. Each unwittingly wants the other woman’s real-life love.

Guglielmo finds Dorabella surprisingly easy to win over. Fiordiligi has more willpower, but her attraction to Ferrando leaves her in an agony of guilt.

The two men compare notes. Guglielmo gloats, but Ferrando is sickened that he has been betrayed — deceived by Dorabella, and also rejected by Fiordiligi. Alfonso goads him into one last attempt, and this time Fiordiligi’s resolve crumbles. Guglielmo is appalled. Both he and Ferrando admit that Don Alfonso was right: così fan tutte – all women are the same.

The sisters are ready to marry their new lovers (with Despina disguised as a lawyer) when they hear the sound soldiers returning. Their panic turns to shock when they finally realise that the foreign strangers were Guglielmo and Ferrando all along! Don Alfonso has won his bet.