As a storm rages, Siegmund the Wälsung, exhausted from pursuit by enemies in the forest, stumbles into an unfamiliar house for shelter. Sieglinde finds the stranger lying by the hearth, and the two feel an immediate attraction. But they are soon interrupted by Sieglinde's husband, Hunding, who asks the stranger who he is. Calling himself "Woeful," Siegmund tells of a disaster-filled life ("Friedmund darf ich nicht heissen"), only to learn that Hunding is a kinsman of his foes. Hunding, before retiring, tells his guest to defend himself in the morning. Left alone, Siegmund calls on his father, Wälse, for the sword he once promised him. Sieglinde reappears, having given Hunding a sleeping potion. She tells of her wedding, at which a one-eyed stranger thrust into a tree a sword that thereafter resisted every effort to pull it out ("Der Männer Sippe"). Sieglinde confesses her unhappiness to Siegmund, whereupon he ardently embraces her and vows to free her from her forced marriage to Hunding. As moonlight floods the room, Siegmund compares their feeling to the marriage of love and spring ("Winterstürme"). Sieglinde hails him as "Spring" ("Du bist der Lenz") but asks if his father was really "Wolf," as he said earlier. When Siegmund gives his father's name as Wälse instead, Sieglinde rapturously recognizes him as Siegmund, her twin brother. I have seen you before. The Wälsung now draws the sword from the tree and claims Sieglinde as his bride, rejoicing in the union of the Wälsungs. High in the mountains, Wotan, leader of the gods, tells his warrior daughter Brünnhilde she must defend his mortal son Siegmund. Leaving joyfully to do his bidding ("Hojotoho!"), the Valkyrie pauses to note the approach of Fricka, Wotan's wife and the goddess of marriage. Fricka insists he must defend Hunding's marriage rights against Siegmund, ignoring Wotan's implied argument that Siegmund could save the gods by winning back the Rhinegold from the dragon Fafner before the Nibelung dwarfs regain it. When Wotan realizes he is caught in his own trap - his power will leave him if he does not enforce the law - he agrees to his wife's demands. After Fricka has left in triumph, the frustrated god tells the returning Brünnhilde about the theft of the gold and Alberich's curse on it ("Als junger Liebe") Brünnhilde is shocked to hear her father, his plans in ruins, order her to fight for Hunding. Then, alone in the darkness, she withdraws as Siegmund and Sieglinde approach. Siegmund comforts the distraught girl, who feels herself unworthy of him, and watches over her when she falls asleep.