Scene 1: Near Thebes
A melodrama (Introduction and Melodrame) opens the work. Public Opinion explains who she is - the guardian of morality ("Qui suis-je? du Théâtre Antique"). She seeks to rework the story of Orphée (Orpheus) and Eurydice - who, despite being husband and wife, hate each other - into a moral tale for the ages. However, she has her work cut out for her: Eurydice is in love with the shepherd, Aristée (Aristaeus), who lives next door ("La femme dont le coeur rêve"), and Orphée is in love with Chloë, a shepherdess. When Orphée mistakes Eurydice for her, everything comes out, and Eurydice insists they break the marriage off. However Orphée, fearing Public Opinion's reaction, torments her into keeping the scandal quiet using violin music, which she hates.
We now meet Aristée - who is, in fact, Pluton (Pluto) - keeping up his disguise by singing a pastoral song about those awful sheep ("Moi, je suis Aristée"). Since Pluton was originally played by a famous female impersonator, this song contains numerous falsetto notes. Eurydice, however, has discovered what she thinks is a plot by Orphée to kill Aristée, but is in fact a conspiracy between him and Pluton to kill her, so Pluton may have her. Pluton tricks her into walking into the trap by showing immunity to it, and, as she dies, transforms into his true form (Transformation Scene) Eurydice finds that death is not so bad when the God of Death is in love with you ("La mort m'apparaît souriante"), and so keeps coming back for one more verse. They descend into the Underworld as soon as Eurydice has left a note telling her husband she has been unavoidably detained (Descent to the Underworld).
All seems to be going well for Orphée until Public Opinion catches up with him, and threatens to ruin his violin teaching career unless he goes to rescue his wife. Orphée reluctantly agrees.
The scene changes to Olympus, where the Gods sleep out of boredom ("Dormons, dormons"). Things look a bit more interesting for them when Diane (Diana) returns and begins gossiping about Actaeon, her current love ("Quand Diane descend dans la plaine"). However, Jupiter, shocked at the behaviour of the supposedly virgin goddess, has turned Actaeon into a stag. Pluton then arrives, and reveals to the other gods the pleasures of Hell, leading them to revolt against horrid ambrosia, hideous nectar, and the sheer boredom of Olympus ("Aux armes, dieux et demi-dieux!"). Jupiter's demands to know what is going on lead them to point out his hypocrisy at great length, describing - and poking fun of - all his mythological affairs. However, little further progress can be made before news of Orphée's arrival forces the gods to get onto their best behaviour. Pluton is worried he will be forced to give Eurydice back, and, after a quotation from Gluck's Orfeo ed Euridice sends the gods to tears, Jupiter announces that he is going to Hell to sort everything out. The other gods beg to come with him, he consents, and mass celebration breaks out at this holiday ("Gloire! gloire à Jupiter").
Eurydice is being kept locked up by Pluto, and is finding life very dull. Her gaoler, a dull-witted tippler by the name of John Styx, is not helping, particularly his habit of telling, at the slightest provocation, all about how he was King of the Beotians until he died. But if he had not died, he would still be king ("Quand j'étais roi de Béotie").
Jupiter spots where Pluton hid Eurydice whilst being shown around by him, and slips through the keyhole by turning into a beautiful, golden fly. He meets Eurydice on the other side, and sings a love duet with her where his part consists entirely of buzzing ("Bel insecte à l'aile dorée"). Afterwards, he reveals himself to her, and promises to help her, largely because he wants her for himself.
The scene shifts to a huge party the gods are having in Hell, where ambrosia, nectar, and propriety are nowhere to be seen ("Vive le vin! Vive Pluton!"). Eurydice sneaks in disguised as a bacchante ("J'ai vu le dieu Bacchus"), but Jupiter's plan to sneak her out is interrupted by calls for a dance. Unfortunately, Jupiter can only dance minuets which everyone else finds boring and awful ("La la la. Le menuet n'est vraiment si charmant"). Things liven up, though, as the most famous number in the operetta, the Galop Infernal (best known as the music of the Can-can) starts, and everyone throws himself into it with wild abandon ("Ce bal est original").
Ominous violin music heralds the approach of Orphée (Entrance of Orphée and Public Opinion), but Jupiter has a plan, and promises to keep Eurydice away from him. As with the standard myth, Orphée must not look back, or he'll lose Eurydice forever ("Ne regarde pas en arrière!"). Public Opinion keeps a close eye on him, to keep him from cheating, but Jupiter throws a lightning bolt, making him jump and look back, and so all ends happily, with a reprise of the Galop.