Laudine's first husband, Esclados the Red, guards the fountain in Broceliande. Yvain comes to avenge the defeat of his cousin Calogrenant and wounds Esclados mortally. The dying knight retreats towards his castle, and Yvain follows so closely that the falling gates trap him inside. Lunete saves the pursuer with an invisibility ring. From hiding he sees the widow's mourning and falls in love with her. Laudine's grief is therefore set beside the desire of the very man who has caused it, a tension the romance does not resolve by pretending that her first husband was unimportant.

Lunete makes a practical argument: the fountain and the surrounding lands still need defence, especially because King Arthur intends to visit the marvel. Laudine initially rejects the suggestion of accepting her husband's killer. Her handmaid nevertheless asks who could protect her more effectively than the knight who defeated Esclados. Yvain is eventually brought before her and offers his service. With the support of her household and barons, Laudine marries him. Arthur's arrival and festive reception follow the marriage; they are not simply the same occasion as the wedding itself.

During the royal visit, Sir Gawain urges Yvain not to abandon tournaments and companionship after marriage. Yvain asks his wife for leave, and she grants it for one year. Her warning is clear: remaining away beyond the deadline will cost him her love. She allows for genuine hindrance when he raises that concern and lends him a ring whose protection is linked to loyal love and remembering her. This is a different ring from Lunete's earlier gift of invisibility. The promise, not possession of jewellery alone, holds the arrangement together.

Yvain stays away too long. At a gathering with Arthur and the knights he realises that he has broken his word, and Laudine's messenger arrives to denounce his failure and take back the ring. The narrative presents his collapse as grief and self-reproach, not as an explicit curse that Laudine casts by removing the object. He withdraws into the wilderness and loses his senses. After his recovery, his service to others earns him the name Knight of the Lion, but neither his recovery nor his new reputation immediately repairs the marriage.

Yvain later rescues Lunete from an accusation of treason without revealing his identity to Laudine. Near the romance's conclusion he returns to the fountain and raises another storm. Lunete persuades her mistress to seek the Knight of the Lion as a defender, but first secures an oath that she will help him regain his own lady's favour. Laudine does not yet know that the estranged wife is herself. When Lunete reveals the truth, Laudine protests at the arrangement but honours her promise; Yvain acknowledges his fault and asks forgiveness. Their reconciliation restores both marriage and guardianship. Related German, English and Welsh retellings alter names and emphasis, rather than supplying additional episodes in one uninterrupted biography.