Mime has set up a metal forge in a deserted area near the spot where a transformed Fafner guards the treasure. Siegfried demands a sword from Mime, but every weapon the Nibelung forges is easily shattered by Siegfried. Commanding Mime to reforge the fragments of a sword purportedly left to Siegfried by his deceased mother, the young man learns more from Mime about his heritage. Wotan, who now wanders the world incognito, approaches Mime and challenges him to a battle of wits, proposing that they each pose three questions to the other. When Mime is unable to answer the final question, Wotan reveals that only a fearless person can reforge Siegfried’s sword, and that person will kill Mime. After Wotan departs, the terrified Mime resolves to teach Siegfried fear in order to save himself. But Mime faces a dilemma: if Siegfried learns fear, who will forge the sword that can kill Fafner and regain the golden hoard? When Siegfried returns to claim his sword, Mime is eager to teach the young man to fear. Siegfried, still immune to fear, successfully reforges Siegmund’s sword and goes off with Mime to reclaim the golden hoard from Fafner. Mime has brewed a poisoned drink to give Siegfried after he triumphs over Fafner.


Alberich, eager to regain the golden hoard, keeps watch near the place where Fafner guards it. Meanwhile Fafner has used the tarnhelm to transform himself into an invincible form. Wotan arrives and warns Alberich of Mime’s designs on the ring and then rouses Fafner so that Alberich may demand the ring from him in exchange for warning him of Siegfried’s approach. Fafner refuses, and Wotan leaves. Siegfried arrives with Mime, who tries to make him fear Fafner. But Siegfried instead resolves to approach Fafner and sends Mime away. Siegfried listens to the birds and fashions a makeshift pipe to imitate them. When the pipe fails to communicate with the birds, Siegfried tries his horn. Fafner emerges and Siegfried kills him. The dying Fafner warns Siegfried against Mime’s treachery, and his lifeblood renders Siegfried instantly able to understand the birds. When Siegfried enters Fafner’s abode, Mime approaches Alberich and the two brothers fight over the golden hoard. Siegfried emerges with the tarnhelm and the ring, and Mime and Alberich hide. A Woodbird warns Siegfried to beware of Mime, who emerges and offers Siegfried the poisoned drink. Now able to understand the true meaning of Mime’s words, Siegfried refuses it and kills Mime. The Woodbird counsels Siegfried to penetrate the wall of fire surrounding Brünnhilde, his destined bride, and offers to lead him to her.


Wotan visits Erda in a last-ditch effort to avert a disastrous future. When she advises him to seek guidance from Brünnhilde, he tells her of their daughter’s disobedience and punishment, and the dismayed Erda becomes unwilling to reveal more. Wotan releases Erda, informing her that he will bequeath the world to Siegfried. Siegfried arrives and Wotan questions him about his sword. Siegfried becomes irritated and tells the old man to leave. Wotan bars Siegfried’s way with his spear, which Siegfried shatters, accusing Wotan of having killed his father. Wotan collects the fragments of the spear as we see him for the last time. Siegfried plunges through the fire and awakens the sleeping Brünnhilde. Though Brünnhilde realizes that she is now a mortal woman and must obey Siegfried, she welcomes him and submits to her fate.