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.
In the poems, Mark is, as a rule, represented in a favourable light, a gentle, kindly man, deeply attached to both Tristan and Iseult, and only too ready to allow his suspicions to be dispelled by any plausible explanation they may choose to offer.
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.
Mark, hunting in the forest, comes upon them sleeping in a cave, and as Tristan, who knows that the king is in the neighbourhood, has placed his sword between them, is convinced of their innocence.
Eventually Mark surprises the two under circumstances which leave no possible room for doubt as to their mutual relation; Tristan flies for his life and takes refuge with Hoel, duke of Britanny.