Finally, King Arthur returns from France and Lancelot and Guenever's bliss is destroyed—but not because of Arthur's return. Sir Bors (Lancelot's cousin) had also just returned to court from visiting King Pelles and brings news that Elaine has given birth to a son and named him Galahad (Lancelot's first name).
In giving birth to Lancelot's son, Elaine draws attention to something uncommented upon previously—Guenever's continued childlessness.
Later that evening, when alone together, Guenever confronts Lancelot: she accuses him of lying to her, of being in love with Elaine and keeping it a secret. Lancelot tries to explain, about the butler and the deceit, and that he hadn't been able to tell her because he didn't want to hurt her. Eventually the two reconcile, but their relationship is forever changed. They love one another more than ever, but their love is bound in hatred, jealousy and betrayal.
This fundamental change in the lovers' relationship will continue to plague both the two and the entire court—Guenever's jealousy and mistrust, and Lancelot's son with another woman.