At Windsor Castle, King Richard summons two quarreling nobles: Henry Bolingbroke, the Duke of Hereford, accuses Thomas Mowbray, Duke of Norfolk, of treason. Bolingbroke says that Mowbray has been plotting against the king for many years and that he was responsible for the murder of the Duke of Gloucester, uncle of both the king and Bolingbroke.

Richard claims to be impartial and he listens to what each man says. Mowbray repudiates the accusation and says that Bolingbroke is lying. Richard tries to get them to calm down and be reconciled but, when he sees this is not possible, he acquiesces in their desire for a trial by combat. He commands that the trial take place at Coventry on Saint Lambert’s day in September.

Bolingbroke’s father, John of Gaunt, Duke of Lancaster, talks with the Duchess of Gloucester, the murdered duke’s widow. Gaunt is reluctant to pursue the murderers of his brother and the duchess fiercely reproaches him for his inaction. She says it is cowardice not to seek vengeance against the murderers—if he does not, he may end up being murdered himself. Gaunt still resists, saying that vengeance must be left to God. The duchess eagerly awaits the combat between Bolingbroke and Mowbray, hoping it will result in Mowbray’s death.