In 14th century France, Norman knight Jean de Carrouges (Matt Damon) accuses squire Jacques Le Gris (Adam Driver) of raping his wife Marguerite (Jodie Comer). When Jacques denies the accusation, many doubt Marguerite's version of the events, leaving her reputation in shatters.

Against Marguerite's wishes, Jean decides to challenge Jacques to a duel to the death, even though he knows that if he loses, it will leave his wife in a precarious position.

Based on the book The Last Duel: A True Story of Trial by Combat in Medieval France by Eric Jager.