I lay down a challenge: If a person here present, within these premises is big or bold or red-blooded enough to strike me one stroke and be struck in return.
The Green Knights hops off of his horse and hands Gawain his axe and places himself in position to be beheaded. Gawain swings and lops off the Knights head, but the knight lives and picks up his decapitated head,gets on his horse and rides away.
I, Arthur will..
Who is brave enough to challenge me.
I, Sir Gawain accept your challenge.
One year later nearing the end of the challenge. Gawain has been searching the lands for the past year to find the Green Knight.
Gawain arrives at a castle and asks the Lord that lives their if he may stay for 3 days and the Lord agrees on the condition that everything he gets in those 3 days he give to him.
The lady of the castle tries for 3 days to make him accept gifts from her but he denies her and on the last day he accepts a magical sash that will make it impossible for somebody to harm him.
I need that sash even if its not Honorable.
Please accept this magical sash of invincibility as a gift.
Gawain finds the Green Knight and is struck over the neck by his axe and survives thanks to the sash. The Green Knight reveals himself as the Lord and this was all a test. Gawain feels terrible that he sacrificed his honour for his life and the Lord tells him it was only natural.