The film is based on the story "Sir Gawain and the Green Knight", which tells the story of King Arthur holding a banquet in his own court. A Green Knight comes to challenge the Knights of the Round Table: who dares to chop off his head on the spot, and asks him to return the axe one year later. Gawain accepts the challenge and chops off the head of the Green Knight. The still-living body picks up the head and returns to the Green Church. One year later, Gawain keeps his promise to find the Green Knight.