Tristan waited in Wales for his uncle to summon him back onto his court. With excitement running through his veins he thought of how wonderful it was going to be to see his love, Iseult without secrecy.
Tristan was shortly summoned by his uncle. As soon as he made it back to his his uncle King Marks residence, he ran straight to the stair steps where he and Iseult used to meet to greet her.
In the middle of a deep hug with one another, the door swung open and the king walked in. Astonished the two began to make up small talk as if they had just been talking, King Mark clearly did not buy the act and ordered them into his quarters to discuss the matter.
King Mark allowed them to explain themselves, but their excuses were not good enough. They eventually came clean and told him the truth.
The king had them thrown in the dungeon till death, he had told them that if they wanted to be together so badly then they may have their last moments in life together.
After their deaths the king had his gaurds bury their bodies somewhere on the kingdoms grounds but unmarked. They were buried together where a oak tree began to grow days later.