King Philip of Spain is jealous of his more popular brother, Don John, and sends him into battle against the Moors, hoping he will not return. Don John is in love with Dolores, daughter of General Mendoza, but the general discourages her, as Don John is betrothed to the Queen of England's sister. Don John returns victorious, and following a dispute over a secret letter, the king stabs his brother and leaves him for dead. When Mendoza accepts the blame, Dolores, who knows the truth, tells the court she had been dishonored by Don John, causing her father's reaction. Dolores then threatens the king that she will reveal his guilt unless her father is pardoned. The king pardons Mendoza, Don John recovers, and he and Dolores marry.