Sir Gawain and the Green Knight Summary
Sir Gawain and the Green Knight tells the story of Sir Gawain as he agrees to a challenge from the Green Knight and returns from it humbled.  
The Green Knight challenges any man to deal him a blow. The Knight will return the blow the following year. Gawain agrees.
Later, Gawain departs to meet the Knight. He agrees to give Lord Bertilak anything he receives while staying at his castle but keeps a girdle Lady Bertilak gives him that will supposedly protect him.  
Gawain finds the Knight, who merely nicks his neck and reveals himself to be Lord Bertilak. He nicked Gawain’s neck because Gawain did not give him the girdle.