Four knights break sanctuary to brutally murder Archbishop Thomas Becket for their king, Henry II. Running from their crime, the four knights - Hugh de Morville, William de Tracy, Reginald FitzUrse and Richard le Brett - flee north to Knaresborough Castle where Morville is overlord. Initially celebrating ridding their king of the pest that Becket had become, they find themselves increasingly isolated as the Church and public opinion turn against them. August is feva time - a celebration and festival of the arts. The Castle Players are to perform a play of their own creation: Knight of Betrayal, based on the events leading up to Becket's murder. Taking the honour very seriously, they work hard to get into character - but are they channelling more than just the characters of the knights they are portraying? As the group of friends begins to disintegrate, concern becomes certainty - this is one opening night that will never be forgotten as life in the small Yorkshire market town of Knaresborough tumbles into horror.