Isolde, an Irish princess, is traveling with her maid Brangäne to the court of King Marke of Cornwall, whom she is to marry. She is accompanied by Marke’s vasal and friend, Tristan, a hero of Cornwall. He decapitated Morold, Isolde’s lover, when Morold tried to collect taxes in Cornwall. Morold’s head was sent back to England. During the fight, however, Tristan was wounded, and Isolde is the only one who knows the secret of healing the wound. Therefore, Tristan returns to Ireland incognito. Isolde successfully treats his wound, but gazing into Tristan’s eyes awakens her love for him.

I.

As the ship approaches Cornwall’s coast, Isolde’s remorse grows. She curses Tristan and wants revenge for the pain he has caused her. He is willing to meet her to repent for his deed. Isolde has prepared a so-called cup of reconciliation, but has ordered it to be filled with a deadly magic potion. Fearing death, Brangäne refuses to follow Isolde’s instructions. She fills the cup with a love potion instead. When Tristan and Isolde drink from the cup, their love is rekindled, and they are condemned to loving one another.

II.

The wedding of Isolde and King Marke has taken place. This, however, does not stop Isolde from secretly living her love for Tristan. They plan a nocturnal encounter when the court is away hunting. The lovers passionately embrace, enjoying this unique moment of togetherness. They glorify night and love, and even prefer love after death to being separated in life. Despite Brangäne’s warning, the lovers are discovered by the returning hunting party. Marke is deeply disappointed by the betrayal of his friend and his young wife. In an attempt to restore the King’s honour, Melot wounds Tristan.

III.

Kurwenal, Tristan’s confidant, has brought him to Kareol, the castle of his youth. He has sent a messenger to Isolde to come and heal Tristan. In the meantime, Tristan sees his life passing by in a fever dream. When Isolde finally reaches the castle, she is too late: Tristan dies in her arms. Having been told the truth by Brangäne, Marke hastens after Isolde by boat. His attempt at forgiveness, however, comes too late. Isolde has found her salvation by uniting with Tristan in death, beyond the strictures of life.