Siegfried, whom Siegmund had fathered with his twin sister Sieglinde, is forging a new Nothung, his father's sword that had broken on Wotan's spear. With this weapon he kills Fafner and his own foster father Mime, Alberich's brother, and now has the ring of power, but he knows no fear and is therefore free from the curse of the Nibelung.
Guided by the voice of nature, Siegfried sets off to Brünnhilde's rock. Wotan opposes him, but the sword Nothung smashes Wotan's spear. Siegfried awakens Brünnhilde and wins her love.