During the trip across the Irish Channel, Tristram entertains Princess Iseult with songs and tales, until he becomes so thirsty that he begs for a drink.  By mistake the love-potion is brought, and, as Iseult graciously dips her lips in the cup before handing it to her entertainer, it comes to pass both partake of the magic draught, and thus become victims of a passion which naught can cure.  Still, as their intentions remain perfectly honorable, they continue the journey to Cornwall, and, in spite of all he suffers, Tristram delivers the reluctant bride into his uncle’s hands.

Some legends claim that Iseult made her maid Brengwain take her place by the king’s side on their wedding night, and that, although the Irish princess dwelt in the palace at Cornwall, she never proved untrue to her lover Tristram.  The romances now give us stolen interviews, temporary elopements, and hair-breadth escapes from all manner of dangers.  Once, for instance, Iseult is summoned by her husband to appear before the judges and clear herself from all suspicion of infidelity by taking a public oath in their presence.  By Iseult’s directions, Tristram, disguised as a mendicant, carries her ashore from the boat, begging for a kiss as reward.  This enables the queen to swear truthfully that she has never been embraced by any man save King Mark and the mendicant who carried her ashore!

Tristram—­like Launcelot—­deeply feels the baseness of his conduct toward his uncle and often tries to tear himself away, but the spell of the magic potion is too powerful to break.  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.  Most of the versions, however, declare that the lovers were buried side by side, and that creepers growing out of their respective graves twined lovingly around each other.