The play is a re-enactment of the conflicts between King Henry II and Thomas Becket as the latter (Henry's best friend) ascends to power, becoming the King’s enemy.
Becket is the King's right hand man; clever, calculating and incapable of love the only quality Becket is unable to perfect is honor. Being a bastard and a saxon, honor is something he assumes he will never know. He bases his decisions on their aesthetic value rather than moral justification and seeks to be a form of stability to the King's erratic behavior. When the King and Becket come upon some peasants the King shouts at them as dogs and demands the daughter be taken to the palace for their pleasure. As the King rides away Becket tells the peasants to hide better next time and throws them a bag of coins for their troubles. Later when Becket is forced to give the King his mistress, Gwendolyn, for the King's amusement, the King brings in the peasant girl Becket was trying to protect and Becket decides he might as well go along with it and tells her to undress...when the King comes running in to say Gwendolyn has killer herself, being the first person who has truly been able to defy the King.
Nervous that the Church will grow too strong for the King to compete with, he decides to make Becket the Archbishop of Canterbury and allow the King to control the Church. Although he proffers his love for Becket, his love is a controlling, demanding love making everyone that succumbs to his love his pawn...and Becket denies him this pleasure. Upon his coronation as Archbishop, Becket becomes for the first time in his life free from all obligation except those of God, he is transformed into an ascetic who does his best to preserve the rights of the church against the king's power.
Ultimately, Becket is slaughtered by several of the king's nobles, and the king is then forced to undergo penance for the murder, mourning the death of the only person he truly loved.