Julius Caesar, Rome's most powerful general, returns victorious and is feasted by the people, while some Romans fear that he will accept the crown and end the Republic. The play tells, in five acts, how the conspiracy is born, kills Caesar, and is destroyed by what it itself unleashed.
Act I
The tribunes Flavius and Marullus drive from the streets the craftsmen celebrating Caesar's triumph and go to strip the decorations from the statues (Scene 1). At the Lupercal procession, a soothsayer warns Caesar against the Ides of March, and Cassius, alone with Brutus, says that Rome bows to a weak man. Brutus, who loves Caesar, admits he fears the people will make him king. Casca tells that Antony offered Caesar a crown three times and that he refused it, and Cassius decides to forge letters to push Brutus (Scene 2). On a night of storm and portents, Casca, frightened, meets Cicero; Cassius, who walks with his breast bared under the lightning, wins Casca over to the conspiracy on learning that the Senate wants to crown Caesar the next day, and Cinna carries the letters that Brutus will find (Scene 3).
Act II
In the early morning of the Ides, Brutus, sleepless in the orchard, concludes that Caesar must die for what he might become, and Lucius hands him an anonymous letter calling him to act. Cassius arrives with the conspirators, hooded; Brutus refuses the oath, excludes Cicero, and prevents Antony from being killed, and they agree that Decius will lead Caesar to the Capitol. Portia demands to know her husband's secret and invokes a wound she made in her thigh, and Brutus promises to tell her and recruits Ligarius (Scene 1). In Caesar's house, Calpurnia, who cried out in her dream that they were killing him, and the augurs, who found no heart in the sacrificed animal, try to keep him from going out. He yields to his wife's plea, but Decius reinterprets the dream and says the Senate will give him a crown that day, and Caesar leaves with the conspirators who came to fetch him (Scene 2). Artemidorus writes a letter denouncing the conspirators and decides to wait for Caesar in the street to hand it over (Scene 3). Portia, anxious, sends Lucius to the Senate to see how Brutus is, and nearly lets slip the cause of her anguish (Scene 4).
Act III
On the day of the Ides, the Soothsayer and Artemidorus try to warn Caesar, who ignores them and enters the Senate. The conspirators surround him under the pretext of a plea from Metellus Cimber; Casca gives the first blow and Brutus the last, and Caesar falls. Antony approaches, pretends alliance, and obtains Brutus's leave to speak at the funeral, against Cassius's advice; alone, he swears vengeance and sends word to Octavius (Scene 1). In the Forum, Brutus justifies the crime in prose: he loved Caesar, but loved Rome more, and is acclaimed. Antony speaks afterward, in verse, praises Brutus and repeats that he is honorable until the phrase becomes an accusation, shows the torn cloak and reads the will, which leaves money to every citizen. The crowd leaves to burn the conspirators' houses, and Antony knows that Octavius has already arrived in Rome (Scene 2). The poet Cinna, mistaken for the conspirator of the same name, is dragged off by the mob, shouting that they should tear him apart (Scene 3).
Act IV
In Rome, Antony, Octavius, and Lepidus mark who must die, and Antony treats Lepidus like an ass that carries gold to wherever its master wants (Scene 1). Near Sardis, Brutus senses Cassius's coldness, and the two enter the tent so as not to quarrel in sight of the soldiers (Scene 2). Inside, Brutus accuses Cassius of selling offices for gold, the quarrel reaches threats, and the two are reconciled. Brutus reveals that Portia has died, news of the proscriptions arrives, and he convinces Cassius to march at once to Philippi. At night, with the servants asleep, he sees the ghost of Caesar, who promises to meet him at Philippi (Scene 3).
Act V
At Philippi, the generals of both sides trade insults, and Cassius, who followed Epicurus, confesses that he has come to give credence to omens; he and Brutus take leave, not knowing whether they will see each other again (Scene 1). Brutus orders the attack at once (Scene 2). Cassius, seeing the soldiers flee, sends Titinius to check whether the distant troops are friends and, believing him captured on Pindarus's report, orders Pindarus to kill him with the sword that killed Caesar. Titinius returns with good news, sees the body, and kills himself, and Brutus mourns the two (Scene 3). In the confusion of battle, the young Cato dies fighting, and Lucilius passes himself off as Brutus so as to be taken in his place (Scene 4). Surrounded, Brutus asks three companions to kill him, and they refuse; he says Caesar's ghost has appeared to him twice, and throws himself on the sword that Strato holds. Antony praises the dead man as the noblest of the Romans, and Octavius orders him given funeral honors (Scene 5).