Siegmund, exhausted, weaponless, and pursued by his enemies, finds shelter from the storm in Hunding’s house, where Sieglinde discovers him lying on her hearth. They are immediately attracted to each other. Siegmund, refreshed, starts to leave so that the ill fate that pursues him will not harm her, but Sieglinde stops him, saying that her life, too, is plagued with misfortune. Her husband Hunding arrives and gradually realizes that Siegmund is the enemy he has been pursuing. Out of respect for the laws of hospitality, he agrees to allow Siegmund to spend the night, but vows to fight him the next day.
Left alone, Siegmund longs for the sword his father (Wotan) had promised to provide at his hour of greatest need. Having drugged Hunding, Sieglinde returns to Siegmund and tells him that on the day she was forced to marry Hunding, a stranger came to her wedding and thrust a sword into the ash tree around which the house was built. Although many have tried, to dislodge it, the sword remains there. Responding to Sieglinde’s eager questions, Siegmund tells enough about himself that she realizes the he is her twin brother. Naming the sword Nothung, Siegmund withdraws it form the tree. Sieglinde identifies herself as his sister. Siegmund claims her as his bride.
Wotan tells his favorite Valkyrie daughter, Brünnhilde, that she will fight for Siegmund in his battle with Hunding. Fricka, the goddess of marriage, objects. Outraged at the incestuous relationship between Siegmund and Sieglinde, she demands that Hunding kill Siegmund. When Wotan explains that the gods need a freely acting hero to regain the ring, Fricka retorts that Siegmund, Wotan’s son by a mortal woman, cannot be a free agent so long as he carries the magical sword Wotan has provided.
When Brünnhilde returns, Wotan tells her that, despite his ambition to use Siegmund to regain the ring, Siegmund must fall in battle. He rages that Alberich and his curse on the ring will cause the doom of the gods. Wotan orders Brünnhilde to fight Hunding.
Exhausted in flight, Sieglinde is comforted by Siegmund. Brünnhilde appears to Siegmund and announces that he will die in his battle with Hunding. When Siegmund hears that he must go to Valhalla without Sieglinde, he prepares to kill his bride first, then himself, so they can remain together in even in death. Deeply moved by Siegmund’s overwhelming love, Brünnhilde stops his upraised sword and promises to protect him in the fight.
When Hunding and Siegmund meet, Wotan sees that Brünnhilde is defying him by protecting Siegmund. Wotan steps in, shattering Siegmund’s sword with his spear and enabling Hunding to kill Siegmund. Brünnhilde gathers the fragments of Siegmund’s sword and flees with Sieglinde. Wotan kills Hunding with a wave of his hand, then pursues his disobedient daughter.
The Valkyries, on their way to Valhalla with the bodies of fallen heroes, are amazed to see Brünnhilde with a woman. Brünnhilde hastily explains that Sieglinde needs asylum from Wotan. The Valkyries suggest sending her to a part of the forest where Wotan never goes. Brünnhilde tells Sieglinde she is to bear a son, Siegfried, who will become the greatest of heroes, and Sieglinde departs, determined to save her son and taking with her the fragments of Siegmund’s sword.
Storming in, Wotan announces that Brünnhilde’s punishment for disobeying him will be the loss of her godhood. She will be put to sleep, to be awakened and claimed by the first man who sees her. Wotan dismisses her eight sisters with the warning that any of them who even come near Brünnhilde again will share her punishment.
Alone with her father, Brünnhilde pleads that she was obeying Wotan’s inner wish even when she broke his command. She begs him to protect her from any unworthy man and conceives the idea that she should be surrounded by fire so that only a hero could wake her. Wotan agrees and sadly kisses her godhood away. He calls upon Loge to surround the sleeping maiden with fire. As the flames appear, Wotan proclaims that only a hero unafraid of Wotan’s spear can claim Brünnhilde.