The PROLOGUE anticipates the song of the love and death of the knight Tristan and the Queen Iseut.
FIRST PART : The Love Potion
Iseut is brought to Cornwall by Tristan on a boat. She is to be married to Tristan’s lord and uncle King Marc against her will.
Using herbs, flowers, and roots, Iseut’s mother secretly brews a magic potion for the couple to be married. She asks Iseut’s companion Branghien to give the couple the drink before their wedding night. The potion is intended only for King Marc and Queen Iseut, so that they can love one another with all their senses in life and death.
On the boat, Iseut is thirsty. Tristan attempts to comfort his future queen. Mistaking the magic potion for wine to quench the thirst, a young servant gives Iseut a filled cup. Iseut and Tristan drink the potion quickly. A passion suddenly enflames between the two, resulting in a love more powerful than all else.
Despairing, Branghien discovers the mistake: She reveals Tristan and Iseut the secret of the potion that brings love and death. All the while, the ship approaches the realm of King Marc.
SECOND PART : The Forest of Morois
King Marc and Iseut marry. Through intrigues, the king learns of the secret love between his Iseut and Tristan. Fleeing the murderous vengeance of the king, the couple hides in the deep forest of Morois, where they lead a harsh life.
One day, King Marc finds the resting couple. But he notices that Tristan’s sword lies between the lovers. Deeply touched, he acknowledges the truth of their love, forgives them and protects them from death at his hand. Awakened from his sleep, Tristan and Iseut acknowledge the grace granted them by King Marc. Conscious of his guilt, Tristan prays for the strength to return the queen to the king. Iseut also regrets her infidelity, and the two decide to part.
THIRD PART : The Death
Duke Hoël offers Tristan Iseut of the White Hands to forget his beloved Iseut. Tristan agrees to the marriage.
One day, Tristan is fatally wounded. His death approaches, and he wishes for his loved one Iseut, for only she could heal him. He asks Kaherdin to bring Iseut his request. Iseut of the White Hands overhears their conversation, and finds out that in case of success, the ship was to fly a white sail, and a black one if Iseut were not aboard.
Fulfilling Tristan’s final wish, Iseut makes her way to her lover. The journey is a rough one. Stormy weather and then a lack of wind make progress difficult. Yet the boat has the white sail raised.
Full of vengeance, Iseut of the White Hands tells the dying Tristan that the approaching boat has raised the black sail. Tristan dies.
When Iseut arrives on land, she can hear the laments and death knolls. On Tristan’s deathbed, she embraces him and dies. Deeply moved by this, King Marc has the two buried side by side.
The EPILOGUE ends the saga, promising comfort in the names of all the authors of this epic that there would be comfort for all lovers: »… from the injustice, from all the grief, from all the pain, from all the pangs of love …«