The Green Knight travels to Camelot in peace to challenge King Arthur's men.
Bertilak invites Sir Gawain to stay at his castle
Sir Gawain accepts the Green Knights challenge and does as he asks. He now has to find the Green Knight in a years time.
Gawain gets into a... well... Sticky situation.
Okay, only three times.
Sir Gawain departs to find the Green Chapel and face the Green Knight once again.
Gawain finds the Green Knight after 1 year
You kept your word, sort of...
However, Sir Gawain does not follow his command.
You may stay with us as long as you give me anything you receive in the castle
Bertilaks wife also gives Gawain a magical girdle, in which he doesn't return like he asks
Bertilak ends up being the Green Knight and commends Gawain for keeping his word. However he confronts him for not returning the girdle. He forgives him for it because Gawain was only trying to protect himself.