The Green Night storms in King Arthur's court and presents him with a challenge. The King will have one chance to cut off the Green Knight's head. If he fails to kill the Green Night, the Green Knight will get a chance to cut off Arthur’s head in one year and one day.
“And I will stand still for your stroke, steady on the floor, provided you honor my right, when my inning comes, to repay” (lines 76-78).
Sir Gawain volunteers to take the challenge presented by the Green Knight in place of King Arthur. Gawain explains that he is the weakest and would be the least missed, so it is better for him to take the risk. The Green Knight prepares his body, and Gawain chops off his head. The Green Knight lives and rides away with his head.
“Then Gawain, at Guinevere's side, made to the King a sign: ‘I beseech you, Sire,’ he said, ‘Let this game be mine’” (lines 121-124).
Towards the end of the year, Gawain embarks on an journey to fulfill his pledge. During his treacherous journey, he stumbles upon a castle, and the lord of the castle invites him to stay. The lord’s wife attempts to seduce Gawain, but being a loyal knight he is able to resist the temptation. The lord exchanges him his game for his wife’s kisses.
“Many men know me, the Knight of the Green Chapel; therefore if you seek to find me, you shall not fail” (lines 185-186).
The wife tries to give Gawain a golden ring, however he refuses to accept the luxurious gift. Since he doesn’t take the ring, she offers him an enchanted sash. This magical sash has the power to grant him invincibility. He humbly accepts the sash as a gift, and in return gives a kiss.
“As long as he keeps it looped around him, no man under Heaven can hurt him, whoever, may try for nothing on earth, however uncanny, can kill him” (lines 133-135).
Gawain goes out to find the Green Knight, and he hides the sash under his clothes. He’s ready to face his destiny and prepares himself for the Green Knight.
“Quickly then the man in the green made ready, grabbed up his keen-ground ax to strike Sir Gawain” (lines 251-252).
The Green Knight swings his ax, but he doesn’t take off Sir Gawain's head. The Green Knight is respectful of Gawain’s honor and nobility. He explains how he himself is the lord of the castle, and that he is happy that Gawain was respectful towards his wife. The sash actually belongs to the Green Knight.
“For you kept our pact of the first night with honor, and abided by your word and held yourself true to me, giving me all you owe das good as man should” (lines 339-341).