Wotan’s son by a mortal woman, Siegmund, flees his foes and ends up in the house of Hunding. He falls in love with Sieglinde, Hunding’s wife, who returns his love. When Hunding comes home, he reveals that he is one of Siegmund’s enemies but admits that he is compelled by laws of hospitality to give Siegmund shelter for the night. Sieglinde drugs her husband. She shows him a sword buried in a tree by a stranger (Wotan in disguise). Siegmund pulls it from the tree. The two fall into each other’s arms. They now know that they are the Volsung twins, separated long ago by the death of their mother, but their ardor still burns bright.
In the gods’ domain, Brünnhilde, the daughter of Wotan, prepares on his orders to fight for Siegmund against Hunding. Fricka, Wotan’s wife, argues that Wotan must destroy his son because of Siegmund’s incest, which is against the laws of the gods. Bound by his own promises to honor the laws, Wotan countermands his order to Brünnhilde. However, when she meets Siegmund and Sieglinde, Brünnhilde decides to defy Wotan. Wotan has to appear himself to give Hunding the victory over Siegmund, shattering Siegmund’s sword during the battle. Gathering up the fragments of Siegmund’s sword, Brünnhilde helps Sieglinde escape.
Enraged at Brünnhilde, Wotan pursues the Valkyrie and sentences her to become a mortal. Brünnhilde persuades her father to place her in an enchanted sleep and surround her with fire so that only a fearless man can win her.