Act 1The Spanish Tragedy begins with the ghost of Andrea, a Spanish nobleman, and the personified abstraction of Revenge. Andrea explains that he was killed in battle against the Portuguese. This deprived him of his secret love, Bel-Imperia, and his ghost has now emerged from the underworld to seek revenge. Revenge promises the ghost of Andrea that he will witness his killer, Prince Balthazar, killed by Bel-Imperia. These two characters remain on stage throughout the play.At the Spanish court, a general explains that during the battle, Balthazar was defeated in single combat by Horatio and taken prisoner. This ensured Spain's victory, and Portugal has agreed to pay Spain tribute. Balthazar is treated leniently, being merely detained in Spain as the guest of Lorenzo.At the Portuguese court, the viceroy of Portugal is deceived by Villuppo into believing Balthazar is dead.Back in Spain, Horatio tells Bel-Imperia of the circumstances of Andrea's death, and she transfers her affections from Andrea to Horatio, who was Andrea's friend. She also vows to have vengeance on Balthazar. Balthazar, encouraged by Lorenzo, declares his love for Bel-Imperia, but she rebuffs him.The king of Spain holds a banquet, attended by the Portuguese ambassador, to celebrate the new alliance between the two countries. The ghost of Andrea complains to Revenge at seeing Balthazar so well received at the Spanish court. Revenge tells him that friendship will soon turn into enmity.Act 2Lorenzo, trying to advance Balthazar's cause with Bel-Imperia, gets her servant Pedringano to admit that she is in love with Horatio, because he has seen letters she sent to him. Lorenzo promises Balthazar that he will get rid of Horatio, leaving Balthazar free to win Bel-Imperia's love. In scene 2, Balthazar and Lorenzo, helped by Pedringano, spy on Bel-Imperia as she and Horatio discuss their love for each other. The new lovers arrange to meet in secret at night, in a garden on Horatio's father's land, where they will not be disturbed.After a scene in which the duke of Castile agrees to the marriage of his daughter to Balthazar, Lorenzo and Balthazar, informed by Pedringano, surprise Horatio and Bel-Imperia at their secret meeting. They hang and stab Horatio and abduct Bel-Imperia. The disturbance arouses Hieronimo from his bed, and Hieronimo cuts down Horatio and laments his murder. Isabella, his wife, joins him, and he vows revenge. Meanwhile, the ghost of Andrea is again irritated, because he has seen his friend Horatio rather than his enemy Balthazar killed. Revenge replies that he only has to wait, and he will see Balthazar brought low.Act 3At the Portuguese court, Alexandro is about to be put to death when the ambassador arrives with the news that Balthazar is alive. The viceroy releases Alexandro and condemns Villuppo to death because of his false claims that Balthazar was dead.In Spain, Hieronimo, mourning for his son, receives a letter from Bel-Imperia in which she tells him that Horatio was murdered by Lorenzo and Balthazar. She calls on him to take his revenge. Hieronimo, suspicious that the letter may be a trick, resolves to investigate before he takes action. After Hieronimo talks with Lorenzo, Lorenzo becomes suspicious that Hieronimo may know something about the murder. He fears that Balthazar's servant, Serberine, may have said something to him. Lorenzo pays Pedringano to kill Serberine, but after Pedringano shoots Serberine, he is apprehended by three constables, who take him to Hieronimo. Lorenzo then arranges for Pedringano to be executed, while falsely telling him that a pardon already enacted will be revealed at the last minute (thus buying Pedringano's silence). The scheme goes wrong when the hangman shows Hieronimo a letter he has found on the dead Pedringano's clothing that confirms that Lorenzo and Balthazar killed Horatio. Hieronimo resolves to go to the king and seek justice. In the meantime, Isabella goes mad in her grief over her dead son, and Bel-Imperia, who is being kept in seclusion by Lorenzo, bemoans the fact that Hieronimo has not yet avenged Horatio's death.Lorenzo sends for Bel-Imperia, who rails at him for abducting her. Lorenzo explains that he killed Horatio to protect her honor, since they had met in secret. He reminds her of how her reputation suffered because of her clandestine love affair with Andrea. He also explains that he abducted her lest the king should have found her there. He kept her in seclusion because he wanted to spare her the anger of their father, who is angry at Andrea's death. Balthazar again presses his claim to her love, but Bel-Imperia remains unresponsive.Meanwhile, the grief-stricken Hieronimo contemplates suicide but decides against it, since if he dies there will be no one to avenge Horatio. Meanwhile, the king, the duke of Castile and the Portuguese ambassador agree on the marriage of Balthazar and Bel-Imperia. Hieronimo bursts in, calling for justice, but after he is restrained and ushered away, Lorenzo tries to convince the king that Hieronimo is not only mad but also wants for himself the ransom paid by Portugal for Balthazar.Hieronimo forms a plan for vengeance, but waits until the best time to execute it. Meanwhile, he pretends he knows nothing of the guilt of Lorenzo and Balthazar. However, the grief of a man named Bazulto for his murdered son causes Hieronimo to reproach himself for delaying his revenge.The viceroy arrives for the wedding, and Castile reproaches his son Lorenzo for obstructing Hieronimo's access to the king. When Hieronimo enters, summoned by Castile, Hieronimo pretends to be reconciled with Lorenzo. The act concludes with the ghost of Andrea again calling for revenge. Revenge reassures him, in the process explaining to Andrea the meaning of a "dumb show" (mimed performance) they have just witnessed.Act 4Bel-Imperia reproaches Hieronimo for failing to avenge Horatio and tells him that if he does not act, she will carry out her revenge herself. Hieronimo reassures her that he has a plan, and asks her to join with him. Lorenzo and Balthazar enter and ask Hieronimo to devise some entertainment for the Portuguese ambassador. Hieronimo produces a tragic play that he wrote when he was young. He assigns them all parts. Balthazar is to play Soliman the Turkish Emperor who pursues a woman, Perseda (played by Bel-Imperia), who kills him after one of Soliman's men (played by Hieronimo) kills her husband, Erastus (played by Lorenzo).Isabella, believing that Hieronimo has abdicated his revenge, curses the garden where Horatio was murdered, and then kills herself.The play is acted in front of the Spanish king, the viceroy of Portugal, and other members of the court. At the appropriate moment in the plot, Hieronimo stabs Erastus (Lorenzo). Bel-Imperia stabs Soliman (Balthazar) and then stabs herself. The on-stage audience does not realize the deaths are real, not feigned. Then Hieronimo produces the body of Horatio and explains how Horatio was murdered, and that the deaths of Balthazar and Lorenzo are real, designed by him. Bel-Imperia he had intended to spare, but she took it upon herself to commit suicide. Hieronimo then tries to hang himself. He is restrained, and the king demands that he explain himself fully. Hieronimo refuses to explain what role Bel-Imperia had in the plot, and bites out his tongue rather than speak. A pen is brought for him to write down an explanation. Hieronimo indicates he needs a knife to mend the pen, but when the knife is brought, he stabs the duke of Castile and himself.In the final scene, the ghost of Andrea is pleased by what he has witnessed. He looks forward to welcoming Horatio, Bel-Imperia, Isabella and Hieronimo in pleasant circumstances. Revenge tells him that he can hurl his enemies to the deepest hell, and Andrea picks out the punishments for them that best please him.