Act I
Act I, scene i, of The Tower takes place in front of the tower. The son of King Basilius, Sigismund, who was condemned to be locked in the tower for life because of a prophesy warning the king that his son would one day rise up against him in rebellion, is now twenty-one-years old. Sigismund, unaware of his royal heritage, lives and acts like an animal, locked in a cage and taunted by his keepers. Julian, the tower governor, has called in a physician to examine Sigismund; the physician makes note of his royal bearing. Act 1, scene 2, takes place in a room in the tower. Julian explains to the physician that Sigismund had been accused of murder and without a trial was condemned to death at the age of twelve. Julian had put him in the care of a peasant family until age sixteen, when he locked him in the tower to protect him from being murdered. Julian conspires with the physician to obtain a potion that they can give Sigismund, which will put him to sleep so they can transport him to a monastery for his own safety. Julian pays the physician with a purse of money and a valuable ring for this service.

Act II
Act II, scene I, takes place in the cloisters of a monastery. King Basilius arrives with his attendants, and speaks with Brother Ignatius, the grand almoner, a very old and wise priest. The king explains to Brother Ignatius the prophecy that his son would one day rise against him in rebellion. Brother Ignatius chides the king for his behavior, and the king, in anger, has him taken away. Julian arrives and convinces the king to allow Sigismund a retrial to determine if he is fit to be restored to his proper place as heir to the throne. The king agrees and praises Julian for twenty-two years of loyal service. Act II, scene ii, takes place in a room in the Tower. The peasant woman who raised Sigismund as a child is brought in, informs him that his stepfather has died, and prays with him. Julian then administers the potion that renders Sigismund unconscious.

Act III
Act III takes place inside the queen’s death chamber. Sigismund, restored to his humanity, rides up on a horse. The king grants him the power to succeed as the royal heir to the throne. But Sigismund immediately attacks the king and continues until attendants stop him. The king states that the prophesy has come true, as his son has risen up against him in rebellion. The king then sentences Sigismund and Julian to death for treason.

Act IV Act IV takes place in a hall in the castle. It is the day scheduled for the execution of Sigismund and Julian. On the way to his death, Sigismund is paraded through the streets. A planned rebellion breaks out, the king is ousted, and Sigismund ascends the throne in his place. He is informed, however, that the peasants have not accepted his rule, and, under the leadership of a man named Oliver, are in revolt.

Act V
Act V takes place in an antechamber of the castle. Julian, who has been attacked by the rebels, is brought in to Sigismund, before dying. Oliver, who has taken control of the rebels, enters and challenges Sigismund’s authority. Several of Oliver’s attendants confirm that they have assassinated King Basilius. Oliver announces to Sigismund that he has taken control of the people. Sigismund is shot by Oliver’s men and dies in the arms of Anton and the physician.