Mark, in one of his fits of jealousy, banishes Tristan and Iseult from the court; the two fly to the woods, where they lead an idyllic life, blissfully happy in each other's company.
Unhappily, on the voyage, by some mistake (accounted for in different ways), Tristan and Iseult drink the love drink, and are forthwith seized with a fatal passion each for the other.
There he gives himself out for a minstrel, Tantris, and as such is tended and healed by Queen Iseult and her daughter of the same name.
In this direction lies Chapelizod, said to take its name from that Iseult whom Tennyson, Matthew Arnold and Wagner made a heroine; beyond which is Lucan connected with the city by tramway.
Tristan and Iseult set sail for Cornwall, Iseult accompanied by her waiting-woman, Brangaene (who, in some versions, is also a kinswoman), to whose care the queen, skilled in magic arts, confides a love-potion.
The ship that was to bring Iseult to the mortally wounded Tristram was to hoist a white sail if she was on board, a black sail if she was not.
This is done in the presence of the court; Tristan is pardoned, formally declares his errand, and receives the hand of Iseult for his uncle King Mark.
Ultimately, while assisting his brother-in-law in an intrigue with the wife of a neighbouring knight, Tristan is wounded by a poisoned arrow; unable to find healing, and being near to death, he sends a messenger to bring Queen Iseult to his aid; if successful the ship which brings her is to have a white sail, if she refuses to come, a black.
Iseult of the white hand overhears this, and when the ship returns, bringing Iseult to her lover's aid, either through jealousy or by pure inadvertence (both versions are given), she tells Tristan that the sail is black, whereon, despairing of seeing his love again, the hero turns his face to the wall and dies.
The seneschal of the court, a coward who has been watching for such an opportunity, cuts off the dragon's head, and, presenting it to the king, claims the reward, much to the dismay of Iseult and her mother.