Before the opera begins, Ireland has defeated Cornwall in war
The Irish prince Morold, his weapons blessed by the princess Isolde, travels to Cornwall to claim tribute from King Marke. The King’s nephew, Tristan, fights with Morold and kills him but is wounded himself. He sends Morold’s head (instead of the claimed tribute) to Ireland. Tristan’s wound can only be healed by Isolde, since she had blessed the weapon that wounded him. Disguised as a minstrel, he allows his boat to be swept onto the coast of Ireland. Nursing him, Isolde is gripped by a feverish love – even though she realises he is the man who has killed Prince Morold – and it is reciprocated. Isolde knows she should avenge Ireland’s disgrace – but she cannot. Once healed, Tristan is allowed to return to Cornwall. Some time later, King Marke, whose own wife has died, is persuaded to claim Isolde as his wife. Tristan is sent to Ireland to fetch her. Isolde is mortified that Tristan is doing this.
Act 1 En route from Ireland to Cornwall
Tristan is captaining the vessel but has refused to speak to Isolde. His loyal Kurwenal mocks Isolde about the slaughter of Morold. Isolde tells Brangäne that Tristan has betrayed their love. Brangäne suggests they use a potion to reignite their love. It was amongst the remedies given to them by Isolde’s mother. Isolde asks for a potion of death. Cornwall is in sight and Isolde sends a message to Tristan: she will only allow him to present her to King Marke if first he comes to see her. Isolde asks Brangäne to prepare a death potion for them both; thus Tristan will pay for his betrayal. Tristan explains his aloofness: ‘where I have lived, custom dictates that he who accompanies the bride home must keep his distance from her’. He senses the drink of ‘atonement’ is poisonous – but welcomes it. The two wait for the poison to take effect and they confess their love. Brangäne tells them that she substituted a love potion for the death potion. The lovers are oblivious to everthing apart from one another.
Act 2 King Marke’s palace
Isolde has arranged an assignation with Tristan while her husband is hunting. Brangäne warns Isolde that Melot, Tristan’s supposed friend, has laid a trap;
during the night hunt, King Marke will catch the lovers together. Brangäne won’t signal to Tristan that it is safe. Isolde is impatient and does it herself. Isolde and Tristan are together and welcome the world of Night: the world of passion and ecstasy. The world of Day keeps them apart. Brangäne warns them to be careful. Kurwenal rushes to warn them. King Marke interrupts the lovers. He is not angry, but begs Tristan to explain and reminds Tristan that after the death of his first wife, it was Tristan himself who had urged him to remarry and set about finding a worthy bride. Neither of the lovers will tell Marke about their past encounter and Tristan asks Isolde if she will follow him into the world of Night. Tristan challenges Melot and allows himself to be wounded so that he might finally be released from the agony of Day.
Act 3 Tristan’s family home in Brittany
The wounded Tristan has been brought here by Kurwenal. He has sent for Isolde who alone can drag Tristan back from Night to Day. When the shepherd spots her boat, he will change his soulful tune to a happier one. When Kurwenal tells Tristan that Isolde is on her way, he is ecstatic. Tristan curses the potion that kept them both from death. The shepherd changes his tune. Tristan pulls off his bandages, calls her and dies in her arms. Marke has been told the truth by Brangäne and arrives with Melot to forgive the lovers. Kurwenal mistakenly construes Marke’s approach as vengeful, kills Melot, and dies defending Tristan’s body. Marke laments the death all around him. Isolde describes the ascent of Tristan’s soul and the waves sweeping around her. Transfigured, she joins Tristan in death.