The premise of the story, in short, is that the Green Knight barges in to a feast that Arthur is throwing and tosses down a challenge (and an axe) to the king and his knights: 'come on, one of you take your best swing at me, but then I get to take my best swing in turn, in one year's time.' Gawain takes the challenge, picks up the axe, and decapitates the Knight in one swing--the now-headless Knight reaches down, and picks up his severed head, and says, 'see you in a year,' and rides off. The rest of the story is Gawain, being the honorable knightly sort, traveling to the Green Knight's castle as the one-year deadline approaches to take his lumps.
