As the play begins, the Spanish army has just defeated the Portugese in an epic battle. While the Spanish practiced chivalry by capturing the Portugese prince Balthazar in exchange for ransom, Prince Balthazar did not return the favor, slaying the young nobleman Don Andrea on the field of battle. The goddess Revenge promises Don Andrea’s Ghost redress for this slight. As the King of Spain’s brother, the Duke of Castille, recounts the battle and delivers promise from the Portugese of homage, the Portugese prince is brought captive before the King. Two young men claim reward: Lorenzo, the King’s nephew, and Horatio, son to Hieronimo, a judge who serves the King doubly by arranging royal plays and entertainments. Solomon-like, the King of Spain rewards both young men.
In Portugal, the Viceroy mourns, believing his son Balthazar to have died in battle. When Alexandro tries to give him hope, Villuppo plunges the Viceroy into despair by relating how he witnessed Alexandro shoot Prince Balthazar in the back. Meanwhile Horatio relates Don Andrea’s fate to the dead man’s secret love, Bellimperia, daughter to Castille and sister to Lorenzo. As heir to the throne of Spain (the King being childless), Bellimperia had to hide her love of the lower-ranked Andrea from her father. Knowing that Prince Balthazar seeks her affections, Bellimperia decides to love Horatio, partly to spite the Prince who killed her former love. As Balthazar expresses his love for Bellimperia, the King of Spain entertains the Portugese Ambassador with a masque, an entertainment arranged by Hieronimo. Lorenzo tries to persuade the Prince that Bellimperia will love him, and – bribing and threatening her servant Pedringano – learns Bellimperia loves Horatio. Pedringano brings Lorenzo and the Prince to overhear a love exchange between Bellimperia and Horatio, who plan to meet that night in the arbor in Horatio’s father Hieronimo’s garden.
Meanwhile, the King of Spain arranges a marriage between Bellimperia and Prince Balthazar, promising their heir will rule all of Spain. When Horatio and Bellimperia meet, Lorenzo orchestrates an ambush that leads to Horatio’s death. Hearing the shouts, Hieronimo rushes out to find the corpse of his only son. He and his wife Isabella are distraught.
Back in Portugal, the Viceroy arranges to torture and kill Alexandro, but the Ambassador returns just in time to confirm Villupo’s treachery and tells the Viceroy of the planned marriage. As Hieronimo raves with grief, he receives a letter from Bellimperia written in blood, naming the murderers of his son. When Lorenzo then sees the distraught Hieronimo, he convinces Pedringano that another servant, Serberine, has told Hieronimo everything. Lorenzo arranges for Pedringano to kill Serberine that night. However, he also arranges for the Watch to catch Pedringano in the act. The imprisoned Pedringano writes to Lorenzo for help. Lorenzo sends his Page with a box, reputedly containing Pedringano’s pardon; but the Page (against orders) opens the box and finds it is empty. When Pedringano is brought to Hieronimo’s court of law, he arrogantly confesses to murder and goes laughing to the gallows, expecting his pardon to be revealed at any minute. After his death, the Hangman brings Hieronimo a letter in which Pedringano describes the details of Horatio’s murder and names Balthazar and Lorenzo as the perpetrators. But Horatio’s mother, Isabella, has been lost to grief.
Meanwhile, Lorenzo frees Bellimperia, whom he has locked up, telling her it was for her own good so that she would not be disgraced if it was learned she loved the low-born Horatio. A Portugese contingent, on their way to court, encounters an incensed Hieronimo, who comes before the King but cannot achieve justice, due to Lorenzo’s intervention. Hieronimo decides to pretend insanity. When some citizens come to him in a professional capacity, he tears up their legal documents. The Viceroy of Portugal arrives in Spain to celebrate the truce with the planned wedding. The Duke of Castille warns his son not to treat Hiernomio poorly and all agree old grudges will be forgotten. When the Ghost of Andrea wonders at this accord, Revenge counsels patience. Bellimperia confronts Hieronimo, accusing him of forgetting his son, and she promises to help him revenge Horatio’s death. Hieronimo then enlists Lorenzo and Balthazar as actors in a play to be perfomed as part of the wedding celebration. As the play is performed, Don Andrea gets his wish for revenge, and many truths come to light.