Bors meets Launcelot and accepts his advice to eat only bread and water and to wear no proud knightly clothes but only a plain shirt under his armor. Riding on his way, Bors sees a bird which kills itself for its young. He comes to a castle where a lady asks him to fight as her champion; he agrees to do so, then goes to bed and dreams.
Bors sees a white bird which offers him riches, then a black bird which asks him to serve her tomorrow, for her blackness can do far more for him than the other's whiteness. In a second dream he sees a chapel with a chair in it, on the left of the chair a worm-eater tree, on the right two lilies; the tree desires to take the life from the lilies but is prevented; then from these flowers come many more. A wise man says, "Guard yourself lest any such adventure befall you."
The next day Bors fights for the lady and wins without killing his enemy. As Bors rides on, he finds his brother Sir Lionel naked and bound, being beaten with thorns. The same instant he sees a maiden who is about to be raped. Not knowing which to save, he prays that Christ defend Lionel, then goes to help the lady. He meets a seeming priest who falsely interprets Bors' visions and guides him to a lady who slays herself because he will not lie with her. In that instant the lady, her attendants, her tower, and the false priest all vanish in howling smoke.
A true priest explains that Lionel, a knight who has needlessly killed, is the rotten tree of Bors' vision, while the rapist and threatened maiden are the lilies: in choosing them, Bors has chosen correctly, for they were still sinless, unlike Lionel. The battle he fought as a lady's champion was a battle for the New Law, Holy Church (represented also by the humble black bird of his dream), against the Old Law and the Devil, represented by the outwardly white bird.
Bors leaves and soon meets Lionel, free now and armed. Lionel tries to kill him for his choice of the lady rather than himself, and when a holy man throws himself over Sir Bors to save him, Lionel kills the holy man. He then kills another knight who tries to save Bors, and Bors prepares to kill Lionel. A fiery cloud parts them and Bors is ordered to flee to where Percival awaits him.