the aria Nature, amour, qui partagez mon coeur. If he does what Telaira says and manages to persuade Jupiter to restore his brother to life, he knows he will lose the chance to marry her. But he finally yields to her pleas. Jupiter descends from above and Pollux begs him to bring Castor back to life. Jupiter replies he is powerless to alter the laws of fate. The only way to save Castor is for Pollux to take his place among the dead. Pollux, despairing that he will never win Telaira, decides to go to the Underworld. Jupiter tries to dissuade him with a ballet of the Celestial Pleasures led by Hebe, goddess of youth, but Pollux is resolute. Act 3 The stage shows the entrance to the Underworld, guarded by monsters and demons. Phoebe gathers the Spartans to prevent Pollux from entering the gate of the Underworld. Pollux refuses to be dissuaded, even though Phoebe declares her love for him. When Telaira arrives and she sees Pollux's true love for her, Phoebe realises her love will be unrequited. She urges the demons of the Underworld to stop him entering (Sortez, sortez d'esclavage/Combattez, Démons furieux). Pollux fights the demons with the help of the god Mercury and descends into Hades. Act 4 The scene shows the Elysian fields in the Underworld. Castor sings the aria Séjours de l'éternelle paix: the beautiful surroundings cannot comfort him for the loss of Telaira, neither can a Chorus of Happy Spirits. He is amazed to see his brother Pollux, who tells him of his sacrifice. Castor says he will only take the opportunity to revisit the land of the living for one day so he can see Telaira for the last time. Act 5 Castor returns to Sparta. When Phoebe sees him, she thinks Pollux is dead for good and commits suicide so she can join him in the Underworld. But Castor tells Telaira he only plans to remain alive with her for a single day. Telaira bitterly accuses him of never having loved her. Jupiter descends in a storm as a deus ex machina to resolve the dilemma. He declares that Castor and Pollux can both share immortality. The opera ends with the fête de l'univers ("Festival of the Universe") in which the stars, planets and sun celebrate the god's decision and the twin brothers are received into the Zodiac as the constellation