Wotan has been prey to anxiety ever since he stole the ring from Alberich and used it to pay the giants rather than returning it to the Rhinedaughters. Desperate to protect himself should Alberich regain the ring, he has sought out Erda, who bore him the warrior-maiden Brünnhilde. Brünnhilde and her eight sisters are raising an army of slain heroes to defend Valhalla. Wotan, in the meantime, has also fathered Siegmund and Sieglinde, the Wälsung twins, with a mortal woman. With Siegmund, Wotan hopes to create a free being who will recover the ring, for he fears the curse Alberich placed on him when he violated his own rule of law.
A storm is raging. An exhausted man takes shelter. He asks whose house he is in. Sieglinde brings him water and tells him that the house and she herself belong to Hunding. The stranger tells her he is wounded and unarmed. Sieglinde offers him first water, then mead, which he asks her to share.
Revived, he prepares to go, saying that wherever he roams misfortune follows. Sieglinde begs him to stay, explaining that her life could not be more unhappy. Hunding returns and offers the stranger grudging hospitality. He notices a resemblance between his wife and the stranger. Hunding asks his name. The stranger says it should be Woeful. He tells his tale. He and his father returned home from hunting one day to find their home burnt down, his mother murdered and his twin sister abducted. His father disappeared, and ever since he has been haunted by misfortune. He lost his weapons defending a girl who was being forced into a loveless marriage; he had killed her brothers only to see her killed by others of her clan. Hunding realizes that the murdered men were his kinsmen. Bound by the laws of hospitality, he gives the stranger shelter for the night but challenges his unarmed guest to a fight the next morning.
Alone, the fugitive recalls the sword his father once promised he would find in his hour of greatest need. Sieglinde returns, having drugged Hunding. She recounts how, at her enforced wedding to Hunding, a stranger appeared and thrust a sword into the tree trunk. No one has been able to pull it out. Sieglinde and the stranger now pledge themselves to one another and the stranger asks Sieglinde to rename him. Discovering his father’s name was really Wälse, she is convinced he is her twin; she names him Siegmund and urges him to remove the sword from the tree. Calling it Nothung, he draws it out and claims Sieglinde as both bride and sister. Ecstatically and defiantly, they declare their love.
Wotan instructs Brünnhilde, his favourite Valkyrie daughter, to ensure that Siegmund wins the fight with Hunding. Wotan’s wife Fricka announces that Hunding has appealed to her, as guardian of marriage, to punish the adulterous and incestuous couple. Wotan thinks his children have done no wrong since they love one another: he has no regard for loveless bonds. Fricka demands to know how Wotan can both sanction incest and uphold the supremacy of the gods. He outlines his plan: a hero must develop, Siegmund, who is independent and can carry out the deeds they themselves cannot do. Fricka points out the folly of his argument: Siegmund owes his sword and his life to Wotan; if he were truly independent he would not need the sword’s protection. Defeated, his will broken by this confrontation with his inner truth, Wotan promises that neither he nor Brünnhilde will protect Siegmund.
Alone with Brünnhilde, Wotan gives way to despair. He recounts how, when the pleasures of love started to pall, he began to lust for power and was dishonest in his ruthless pursuit of it. Wotan tells Brünnhilde the story of Alberich, the Nibelung who renounced love and stole the gold from the Rhinedaughters and made a ring from it. Wotan then stole it from Alberich, but instead of returning it to the Rhinedaughters he used it to pay the giants who built Valhalla. He announces that Erda, source of all wisdom, is Brünnhilde’s mother. Brünnhilde and her eight Valkyrie half-sisters were bred to gather up fallen heroes for Wotan, who believes they would protect him from Alberich. Determined that Alberich should never get the ring back, Wotan thought about seizing it from the giant Fafner, who has transformed himself into a dragon. Wotan tells Brünnhilde he could not confront the giant himself because of their contract: he needs a free agent to act for him. When Brünnhilde asks why Siegmund cannot be that hero, Wotan explains that Fricka saw through his duplicity; he has to abandon what he loves most. All he now desires is an ending. But what kind of ending? Wotan tells Brünnhilde that she must not protect Siegmund and threatens the direst consequences if she disobeys.
Siegmund and Sieglinde are fleeing from Hunding. Sieglinde, wracked with guilt, tries to persuade Siegmund to abandon her but he vows to kill Hunding. Brünnhilde appears to Siegmund and announces that he will die in battle and join the other heroes in Valhalla. There he will meet his father. When Siegmund learns that he cannot take Sieglinde he refuses the afterlife. He threatens to kill both Sieglinde and their unborn child, announced by the Valkyrie, rather than be separated from her. Moved by compassion, Brünnhilde promises to safeguard Siegmund.
Hunding’s horn is heard. Brünnhilde tries to protect Siegmund but Wotan shatters Siegmund’s sword with his spear. Siegmund is struck dead. Brünnhilde gathers the pieces of broken sword and flees with Sieglinde. Wotan annihilates Hunding and announces that he will pursue Brünnhilde.