Gutierre is obsessed with the need to preserve his honour and reputation. He marries Dona Mencia, unaware at first that she had been courted by the King's brother. Gutierre is convinced that Mencia is unfaithful and engages a bloodletter to bleed her to death; the King, suspecting his guilt, forces him to marry a previously-abandoned sweetheart. Gutierre warns that he has already been the 'surgeon' of his honour and could be again ...