The narrative begins with the birth of Tristan, an orphan whose mother dies in childbirth, and his eventual arrival at the court of his uncle, King Mark of Cornwall. Tristan proves his worth by slaying the giant Morholt of Ireland, though he is poisoned during the combat and later drifts to Irish shores, where he is secretly healed by Iseult the Fair. Years later, Tristan returns to Ireland to win Iseult as a bride for King Mark, using his cunning to slay a ravaging dragon. During the sea voyage back to Cornwall, Tristan and Iseult accidentally share a potent love potion brewed by the Queen of Ireland.
This philtre binds them in an eternal, consuming passion from which they can never escape. Upon their arrival, Iseult marries King Mark, but she and Tristan continue their secret affair while evading the jealous plots of court barons who seek their destruction. Their secret is repeatedly exposed, leading to dramatic escapes, a sentence of death, and a life of hardship hiding in the wild wood of Morois.
Eventually, Tristan leaves Cornwall for Brittany out of a sense of duty to his uncle, marrying Iseult of the White Hands. However, he remains entirely devoted to his first love. The story reaches its emotional climax when a wounded and dying Tristan sends for Iseult the Fair. Through a tragic deception regarding the color of the ship's sails, Tristan believes he has been abandoned and dies of grief. Upon arriving to find her lover dead, Iseult lies beside him and passes away of a broken heart. King Mark brings their bodies to Tintagel, where a miraculous briar grows from Tristan's tomb and entwines with Iseult's, symbolizing their inseparable bond.
