The King is celebrating Christmas in the castle, surrounded by his court and loyal knights, when suddenly the mysterious Green Knight shows up and offers to accept his challenge. Anyone present can strike a blow at him, but after one year and one day he must meet the Green Knight in a green chapel nine days' journey north and accept the blow in return. Young Sir Gawain, the king's nephew and sole heir, challenges himself to a duel and cuts off the strange visitor's head. But the latter, having put his head back in place, recalls the agreement and departs. A year later, faithful to his word, Sir Gawain sets off to meet his destiny on a journey full of danger.