Based on a book by Anonymous the script follows Gawain (Dev Patel) in a nightmare story that is filled with dark images and a bizarre story.
Gawain accepts a Christmas challenge that requires him to behead the Green Night. The knight after the beheading stands takes up his head while laughing because Gawain must be treated in the same manner on the next Christmas.
Believing the green girdle made by his mother will protect him, as the next Christmas approaches, he takes a trip to the Green Chapel keeping up his end of the oath.
The trip brings him to bizarre locations and visits by strange characters. He retrieves a skull for a woman named Winifred and places it on her dead body. He is ambushed, robbed, and left to die. He also encounters a friendly fox who howls like a coyote and talks. Giants give him advice and he deals with an alluring wife who makes advances toward him.
There is no happy Camelot here, no Galahad or Lancelot, this a dark morbid play that gets curiouser and curiouser as the characters play into odd activities and actions. Eventually we hear off with his head, a line stolen from the Red Queen in Alice in Wonderland.
The Green Night feels like a dark bad trip on drugs and is not much more than a laugh at the end.