"You may be assured by this holly branch I bear That I come to you in peace, not spoiling for battle." (lines 46-47).
Arthur and his knights are gathered to celebrate Christmas and New Years with feasting and partying. Suddenly, an enormous man who is entirely green walks through the door with an elaborately decorated axe.
“I beseech you, Sire,” he said, “Let this game be mine." (lines 118-119).
The man introduces himself as a powerful knight, but he is only here to play a game. He challenges anyone brave enough to swing his ax at the green man's head, and in one year he will return the blow. King Arthur acccepts the challenge at first, but sir Gawain insists that he is the one who participates.
Gawain swings with all his might against the unflinching green knight, and he cuts his head clean off, but the knight picks up his head not phased. He tells Gawain to meet him at a place called Green Chapel in exactly one year, and he rides away with his head in his arms.
Gawain then leaves on a quest to find the Green Chapel to fulfill his pledge and stumbles upon a splendid castle. The lord of the castle welcomes Gawain and invites him to stay with him and his lady for a few days. As the lord goes out to hunt, his lady attempts to seduce Gawain each day, but he resists her. On the third day, she begs him to accept an expensive gift of a ring of gold, but he declines, she then begs him to take a gold sash that was around her waist to remember her by, but he says no again. He finally agrees to taking a magical green sash that will make him indestructible, and he takes it in fear of losing his life to the green knight.
“My lady gay, I can hardly take gifts at the moment; Having nothing to give, I’d be wrong to take gifts in turn.” (lines 195-196).
Gawain returns to the to the green knight at the Green Chapel on New Years, and the knight proceeds with his axe as if he’s going to cut off gawain’s head, but gawain flinches before and the green knight stops and claims that he is a better man than Gawain because he didn’t flinch at all when he received his blow from him.
The green man stops just after barely slitting Gawain's neck and finally tells the truth that he was the lord of the castle that Gawain visited and that he was testing him with his wife the whole time. He tells Gawain that he is the finest man that he knows and admires him for keeping his word, but the only sin he's made was taking the green sash, but he understands because it was in fear of losing his life. Gawain then returns home to King Arthur in Camelot.
"For look how you flinch for fear before anything’s felt! I never heard tell that Sir Gawain was ever a coward! I never moved a muscle when you came down; In Arthur’s hall I never so much as winced. My head fell off at my feet, yet I never flickered; But you! You tremble at heart before you’re touched! I’m bound to be called a better man than you, then, my lord.” (lines 254-261).
"Come to the Green Chapel, I charge you, and take A stroke the same as you’ve given, for well you deserve To be readily requited on New Year’s morn. Many men know me, the Knight of the Green Chapel; Therefore if you seek to find me, you shall not fail. Come or be counted a coward, as is fitting.” (lines 175-180).
"A man who’s true to his word,There’s nothing he needs to fear; You failed me, though, on the third Exchange, so I’ve tapped you here." (lines 332-335).