The Green Knight arrives at the castle amidst the knights festivities. "In the midst of their festivities, an enormous man - who is entirely green - bounds through the door" (210).
The Green Knight asks to play a game with the other men. He proclaims, "That he dares to stoutly exchange one stroke for another, / I shall let him have as my present this lovely gisarme" (lines 69-70).
Sir Gawain says, "Let this game be mine" (line 124). Sir Gawain took on the challenge and striked the Green Knight. After the swing, "The fair head fell from the neck to the floor of the hall" (line 158).
The Green Knight puts his head back on and leaves. He promises to repay the favor to Sir Gawain in one year and a day. Until then, Gawain stays with the a lady in a castle. The lady offers him, "a ring of the yellowest gold" (line 218).
Sir Gawain refuses all of the gifts but one. The lady offers him a satchel which will protect him from all harm. With the satchel, "No man under Heaven can hurt him" (line 234). He wears the satchel and prepares to meet the Green Knight.
Sir Gawain flinches the first time the Green Knight swings. The Knight mocks him saying, "You can't be Gawain" (line 262). The second time Gawain does not move and the Green Knight does not strike because he wanted to test Gawain. The third time, "The sharp blade slit to the flesh" (line 305). The axe does not go all the way though because the Green Knight did not want to kill him. He did not kill him because Gawain respected his wife and only took the sash because he valued his life. The Green Knight respects Sir Gawain and lets him free.