Content Warning: The source material references suicidal ideation.

Rivalin, a knight and feudal lord, attacks a duke named Morgan, forcing him to retreat to his castle. After a prolonged siege, the two negotiate a year-long truce. Following the settlement, Rivalin travels to England to spend time at the court of King Mark and learn his customs.

Rivalin is warmly received in Mark’s court and takes part in a festival not long after his arrival. He participates in a variety of knightly competitions and wins the admiration of Blancheflor, King Mark’s sister. Rivalin likewise falls in love with her, but they are both too bashful to reveal their feelings for one another. After a different king invades Mark’s kingdom, Rivalin helps Mark in battle and sustains an apparently fatal wound from a lance. Blancheflor is overwhelmed by grief, and with the aid of her nurse, she gains admittance to Rivalin’s room disguised as a beggar. She and Rivalin confess their love for each other; Rivalin miraculously recovers, while Blancheflor becomes pregnant.

The two continue to see each other until one day Rivalin receives news that Morgan has invaded his realm. Rivalin is killed in battle, and Blancheflor dies soon after in childbirth.