Once remorse and shame actually drive him mad, and he roams around the country performing all manner of crazy deeds.
He too, when restored to his senses, visits Arthur's court, is admitted to the Round Table, and joins in the Quest for the Holy Grail, which, of course, he cannot achieve.

Then he does marvels in the matter of hunting and fighting, and, having received another dangerous wound, wonders who besides Iseult of Cornwall can cure it?
It is then he hears for the first time of Iseult of Brittany (or of the White Hands), whose skill in such matters is proverbial, and, seeking her aid, is soon made whole.

But meantime the physician has fallen in love with her patient, and fancies her love is returned because every lay he sings is in praise of Iseult! Her brother, discovering her innocent passion, reveals it to Tristram, who, through gratitude or to drive the remembrance of his guilty passion out of his mind, finally marries her.

But even marriage cannot make him forget Iseult of Cornwall.

The time comes when, wounded beyond the power of his wife's skill to cure, Tristram sends for Iseult of Cornwall, who, either owing to treachery or to accident, arrives too late, and dies of grief on her lover's corpse.
Some legends vary greatly in the manner of Tristram's death, for he is sometimes slain by King Stark, who is justly angry to find him in his wife's company.