The four knights in Murder in the Catherdral act as agents of King Henry II and actually carry out the murder of Thomas Becket, Archbishop of Canterbury. At the end of the play, three of the four offer justifications for the murder. The second knight asks that they be pitied, saying they were only following orders for the good of the people of England. The third knight says that the archbishop was a guilty criminal, and so his murder was justified. The fourth knight argues that Becket brought the murder on himself, so in reality, the murder was a suicide.
The play was commissioned by George Bell, the bishop of Chichester, as a protest against the Night of the Long Knives of June 1934, in which Hitler turned on his dear old friend Röhm and had him and others who stood in his way murdered. The knights in the play represent the strongmen in Germany who carried out Hitler's orders and the justifications they used to rationalize their crime.