Tristram was seant by his uncle, King Mark of Cornwall, to fetch Isolde from Ireland to be his uncle's bride. Isolde was not happy about the arrangement but her mother gave Isolde's handmaid a potion that if drunk on their wedding night, would make Mark and Isolde love each other forever. But on the journey back to Cornwall, she and Tristram accidentaly drank the potion themselves. Isolde did marry King Mark but carried on an affair with Tristram. One day they were discovered by Mark lying in a field sleeping with Tristram's sword between them. Mark did not kill them but instead exhcanged his sword for Tristram's. When he discovered that his uncle had found them, Tristram left for Brittany. There he married but was unhappy. When his life was threatened by a wound from war, he sent for Isolde and it was agreed that her arrival would be signaled with a white sail on her ship. On the day of her arrival, Tristram's jealous wife falsely told him that a ship with a balck sail was approaching. Beliveing Isolde dead, Trsitram threw himself on his sword. Isolde followed suit shortly afterwards.
This painting shows the lovers drinking the love potion on the journey back to Cornwall.