King Arthur celebrates the season of Pentecost with his Knights of the Round Table at Carduel in Wales. A knight named Calogrenant tells the story of an adventure that happened seven years previously. He had journeyed far into the forest and met a giant who told him about a spring in a mysterious wood. When water from the spring fell onto a nearby stone a terrifying storm would take place. Calogrenant finds the stone and drops water from the spring onto it. A terrifying storm ensues and when it subsides a mysterious knight appears. He challenges Calogrenant to a duel as he is angry about the damage the storm has wrought. Calogrenant is overthrown and is so humiliated that he never speaks of the incident again until now.
Another knight, Yvain, is Calogrenant's cousin and vows to avenge him. King Arthur, meanwhile, wants to see these mysterious things for himself and invites the knights to accompany him. Yvain is peeves as he wants to avenge his cousin's defeat himself so he steals away from court alone. He eventually meets the giant. He sprinkles water from the spring onto the magic stone and a tremendous storm ensues. As the storm subsides the knight appears and challenges Yvain to a duel. It is an even and brutal fight until Yvain smashes the knight's helmet and splits the knight's skill in two. The knight retreats back to his castle where he dies. Yvan becomes trapped between two portcullis that fall behind and in front of him as he enters the castle. As the knight's men come to avenge their Lord's death, the lady's damsel rescues him by making him invisible using magic rings. She then persuaded the widowed Lady Laudine De Landuc to consider taking Yvain as her husband as he has proved himself a worthy protector of her domain. Yvain has fallen deeply in love with her on sight. Laudine agrees and they are married.
Meanwhile King Arthur has embarked on his adventure and as the giant instructs spills spring water onto the stone and starts a storm. As it subsides a knight appears and challenges. The braggart Sir Kay wants to be allowed to fight and Yvain trounces him easily. Yvain then reveals his identity to the Knights and they are glad to find him alive and well.
Sir Gawain urges Yvain to return to Britain with them to participate in tournaments and prove that he has not keen made weak or cowardly by marriage. Laudinr agrees to him leaving on condition he returns to her within a year. She gives him a set of rings that keep the wearer safe as long as their sweetheart is uppermost in their mind. Yvain is very successful in the tournaments and is enjoying them so much that he forgets to return home in the prescribed time frame. Laudine is angry and sends a damsel to denounce him as a hypocrite and to take back the rings. Yvain is distraught and literally out of his mind with remorse. He goes to live in the woods where a hermit takes care of him until one day a noblewoman, Lady Noroison, finds him sleeping naked beneath a tree. She amounts him with a magic potion that restores his sanity and enables him to become himself again. He determined to regain his lost love and rides out to Laudine at the castle. Whilst on the way there he fights off three evil knights and also rescues a lion who is about to be killed by a dragon. The lion repays this valiant act with loyalty and becomes his companion. This is a symbol of honor for a knight. When he arrives he finds Lunete tied to a stake and about to be burned alive. He frees her and the damsel then pleads for her Lady's forgiveness of both herself and Yvain. She agrees to take Yvain back and also takes in the faithful lion as well.
