Wotan's children Siegmund and Sieglinde, who is unhappily married to Hunding, fall in love with each other. With their incestuous, adulterous love, they violate the guest and marriage laws that Wotan's wife Fricka watches over. Siegmund is therefore supposed to die in a duel with Hunding, but Wotan's daughter Brünnhilde, a Valkyrie, defies her father's will and fights for Siegmund. Wotan is forced to kill Siegmund himself. Brünnhilde is punished by her father: he surrounds her with a wall of fire and sinks her into a deep sleep.