There’s a party at King Arthur’s castle. The knights are having fun. They’re drinking, dancing and laughing their heads off. They know their world and are in control.
Then suddenly a Green Knight enters the hall – a green body with a green beard and green clothes and a green horse – and proposes them a strange game:
“It’s called ‘And next year your head’ and this is how it works: one of you will chop my head off, here and now, and thus gives me the right to reclaim his head one year and a day from now.”
Gawain thinks it’s a game he cannot loose and he chops off the Green Knight’s head. The other knights laugh their heads off.
But the Green Knight gets up, grabs his head and mounts his horse. “A year from now I’ll see you at the Green Chapel, Gawain!”
Bound to his knight’s word of honour, this silly game turns out to be the beginning of a quest that turns Gawain’s world upside down. His identity and existence are put into question.