Act I

The giant Fafner has transformed himself into a dragon and is guarding the ring of the Nibelungs along with the hoard in a cave. Knowing that Fafner can only be killed by Nothung, Mime the smith has brought Siegfried up solely for that purpose and kept the fragments of the sword. Yet Mime himself is unable to forge it anew. The boisterous and guileless Siegfried loathes Mime and cannot believe he is both father and mother to him. The dwarf is evasive and accuses Siegfried of ingratitude; Siegfried increasingly threatens him with violence. It’s only when Siegfried discovers the sword fragments that Mime tells the truth: he had found Sieglinde in the forest; she gave birth to Siegfried and died – leaving him only his father’s shattered sword. Siegfried commands Mime to forge it, and storms out. The dwarf remains behind in despair.

In the guise of a wanderer Wotan enters Mime’s workshop. As Mime tries to get rid of the uninvited guest, Wotan presses him to take part in a battle of wits, staking his own head if he loses. Mime grudgingly agrees and poses three questions, all of which the Wanderer answers right. The latter now demands that Mime in turn wager his head on correctly solving his riddles. Mime is at first able to answer, but stumbles on the third question. Wotan gloatingly reveals the answer to the despairing dwarf: Nothung can only be forged anew by someone who doesn’t know fear. To just such a person Wotan forfeits the defeated dwarf’s head.

All Mime’s attempts to teach Siegfried fear come to naught. Finally he suggests that Siegfried learn it from Fafner the dragon, whose cave lies on the path to the world beyond, which Siegfried wants to explore. The latter now files down his father’s sword, smelts the splinters and reforges Nothung himself. Mime meanwhile prepares a sleeping draught which he’ll give Siegfried once he has killed the dragon. Jubilantly the two of them set off for Fafner’s cave.

Act II

The imp of darkness Alberich is keeping watch outside Fafner’s cave, intent on regaining the ring. Wotan’s appearance revives the old animosity between them. The Lord of Light declares he has no further interest in the ring and suggests that Alberich warn the sleeping dragon of the fearless hero that is approaching – maybe Fafner will reward him for it. The dragon is unperturbed, however, and goes back to sleep. Laughing, Wotan leaves Alberich thirsting for revenge.

As soon as they reach Fafner’s cave Siegfried chases away the dwarf. In the shade of a tree he thinks of his parents and hears a bird singing. He tries to respond by playing on a reed; when that doesn’t work he tries his horn, which wakes Fafner. The lad threatens to attack the dragon if it doesn’t teach him to fear. A fierce fight develops and Siegfried plunges Nothung into Fafner’s heart. As he dies, he tells of his brother Fasolt, whom he killed to get hold of the accursed ring. The warning doesn’t register with Siegfried. But when he pulls his sword out of the dead dragon and puts his blood-smeared hand to his mouth, he finds he understands the voice of the woodbird. Following its advice, he climbs into the cave to fetch the ring and the tarnhelm.

Both lying in wait, Mime and Alberich argue over the coveted treasure. When Siegfried comes back out of the cave, the woodbird warns him of Mime, who inadvertently reveals to Siegfried his hypocritical intention to murder him, whereupon Siegfried strikes him dead. In his solitude, Siegfried is told by the woodbird of the wonderful woman that is lying asleep on a rocky summit surrounded by fire and can only be woken by a fearless hero.

Act III

Wotan is sure that Brünnhilde, whom Siegfried is to awaken, will perform the deed that redeems the world, and he no longer fears his own end. Nevertheless he wakes the all-knowing, primevally wise Erda from her deep sleep and pressures her to answer him. When she denies his divine power, he repudiates her “earth-mother’s wisdom” and consigns her to everlasting sleep.

Then Wotan confronts Siegfried, his grandson, and asks him questions with imperious pride. Siegfried is angered and mocks the old, one-eyed wanderer. When the latter declares he is the guardian of the blazing rock, and blocks Siegfried’s path, he shatters the spear that once slew his father. Wotan withdraws.

Siegfried fearlessly traverses the sea of flame and reaches Brünnhilde, who is asleep in her armour. Only when he removes her shield, helmet and chain mail does he realise with terror that it is a woman. After hesitating shyly, he kisses Brünnhilde awake, and she exuberantly greets the radiant hero. But the force of Siegfried’s desire makes her aware of how ignorantly self-satisfied her hero is and how violable she is. The once divine now mortal woman implores him to leave her be, but ultimately she surrenders to the transports of human love, prefiguring the twilight of the gods.