Gawain is at the round table with all the other knights including his Uncle, King Authur.
Finding the Mentor
A green knight appears and offers a challenge. If someone could cut off his head and he would still live, then he could do the same to whichever knight decapitated him. Gawain volunteers seeking a challenge.
Passing the Threshold
The Green Knight prepares to be beheaded by Gawain. King Author tells him no. Gawain continues to cut off his head and surprisingly the Green Knight lives and challenges him to find him, head for a head.
Tests, Allies, and Enemies
Gawain is invite to a castle by the Green Knight disguised as a Lord. The Lord comforts Gawain and has him stay over for several nights, along with the Lords wife.
The Wife gives Gawain a green girdle, and off he goes away from the castle with the Lord who shows him where the Green Knight lives.
Gawain arrives and the Lord leaves. The Green Knight appears with a shiny axe, ready for his payback.