Brünnhilde sends her lover, Siegfried, off to explore the world keeping only the magic ring he has given her. At the Gibichung castle, he encounters Gunther, Gunther's sister Gutrune, and their half-brother Hagen (whose father is Alberich). Urged on by Hagen, Gunther and Gutrune give Siegfried a drink that makes him forget Brünnhilde and fall in love with Gutrune. Once the potion has worked, Gunther tells Siegfried about the goddess enclosed by flames and asks for Siegfried's help in winning her. In return, Gunther pledges to allow Siegfried to marry Gutrune. No longer remembering Brünnhilde, Siegfried agrees. Not knowing that Siegfried has been drugged, Brünnhilde sees that Siegried has forgotten her and is enraged. She and Hagen convince Gunther to plan Siegfriend's death. In the end, when Brünnhilde sees Siegfried's corpse, she resolves to return the ring to the Rhine and end its curse. She takes the ring and plunges into his funeral pyre. The funeral flames spread to burn Valhalla and destroy the gods. The ring is restored to the Rhine, and Brünnhilde's sacrifice begins the world afresh.