Sir Gawain, a knight of King Arthur's Round Table, accepts a challenge from a mysterious "Green Knight" who dares any knight to strike him with his axe if he will take a return blow in a year and a day. Gawain accepts and beheads him with his blow, at which the Green Knight stands up, picks up his head and reminds Gawain of the appointed time. In his struggles to keep his bargain, Gawain demonstrates chivalry and loyalty until his honour is called into question by a test involving Lady Bertilak, the lady of the Green Knight's castle.