Having defeated the monsterous Morholt (the warrior who has lade waste the land of Cornwall), the young Amorican, Tristan, is crowned defender of the realm by the king, Marc'h. Marc'h quickly comes to see Tristan as the son he never had. However, mortally wounded in the battle, Tristan secretely leaves Cornwall, in order to die far away from King Marc'h, whom he loves so much.
Tristan is found, half-dead, on the banks of the green isle, by the beautiful Yseult. She is the daughter of Donnegahn, who is the king of Ireland - and the sworn enemy of King Marc'h.
Beautiful Yseult's incantations, magic and charms bring the defender of Cornwall back to life. Tristan and Yseult are inseparable and, far away from everything and everyone, savour their perfect love. The idyll, alas, does not last. Donnegahn's soldiers are patrolling the Irish coast. Feeling as if her soul is dying, Yseult sends Tristan back to his own people.
On return to the court of King Marc'h, Tristan is feted as a hero who has cheated death. During the celebrations, the king, who has been widowed for years, announces the end of the fratricidal wars between Cornwall and Ireland. And - to seal the reconciliation between the two countries - he will marry the daughter of King Donneghan. Yseult.
To fetch his future wife from Ireland, King Marc'h charges he in whom he has most faith: Tristan, his adoptive son, his champion and his friend. This son, loved more than ever, does not dare to reveal his love for Yseult.
And so, a legendary triangle begins at Tintagel Castle, of love and lies by turns...