As Caesar and his company walk to the Senate, Caesar passes the soothsayer, who reminds him that the ides of March are not yet passed. Artemidorus tries to get Caesar to read his letter, and says it is personal. Caesar rejects it, saying that personal items should be dealt with last.
Brutus fears that the plot has been discovered when Publius remarks that he hopes their enterprise will thrive. Publius then goes straight to Caesar, and the conspirators fear that he is warning Caesar of the plot. But then they see Publius smiling and notice that Caesar does not react badly to his words.
Meanwhile, Trebonius draws Antony out of the way, and the conspirators prepare to put their plan into action. First, Metellus Cimber kneels and puts his petition to Caesar. But Caesar refuses his request. Metellus Cimber's brother will remain banished. Metellus tries again, and Brutus joins him in his plea, to Caesar's surprise. Then Cassius kneels and joins the appeal to Caesar. But Caesar remains unmoved, declaring that he is as constant as the north star. He prides himself on being unbending.
As Cinna and Decius protest Caesar's decision, Casca is the first to stab Caesar; the others follow, including Brutus. Cinna and Cassius tell the senators and others who witnessed the assassination to run to the streets and proclaim that tyranny is dead and liberty and freedom live. Brutus tries to reassure the horrified onlookers. He also reassures Publius that they intend no harm to him or anyone else, but he should leave because the people may attack the killers and Publius might be caught in the middle of it. He says that no one should have to face the consequences of this deed except those who performed it.
Trebonius enters and informs them that Antony has fled to his house and the whole city is in an uproar. Brutus tells the assassins to cover their arms and swords in Caesar's blood and go to the people proclaiming peace, liberty and freedom.
A servant arrives with a conciliatory message from Antony. Antony says that if Brutus will allow him to come safely, he would like to hear their explanation of why Caesar deserved to die. If Brutus will do this, Antony promises him his loyalty. Brutus agrees to these terms and is confident that he will win Antony's support and friendship.
Antony enters and says he does not know what they intend, but as far as he is concerned they can kill him now if they wish. He cannot think of any better time than this, the hour of Caesar's death, to die himself.
Brutus explains that they acted as they did because of pity for the condition of Rome under Caesar. He adds that they mean no harm to Antony, and Cassius confirms this. Brutus says that they first must calm the populace and then they will explain exactly why they assassinated Caesar. Antony replies that he does not doubt their wisdom, and one by one he shakes the conspirators' hands. But then he praises Caesar and asks forgiveness of him for making peace with his killers.
Cassius tries to find out whether Antony will be one of their supporters. Antony replies that he is their friend, but he still wants to hear how they justify their act. Brutus promises they will.
Antony asks that he may be permitted to speak at Caesar's funeral. Brutus immediately grants this request, but Cassius pulls him aside, saying that they should refuse to let Antony speak, since he may sway people against them. Brutus tries to reassure him by saying that he will speak first and tell the people why Caesar was killed, and will then emphasize that Antony speaks with their permission. The assassins want Caesar to have all the ceremony that is due to him; Brutus says this will rebound to their advantage. Cassius is not convinced, but he does not oppose Brutus's plan. Brutus gives Antony permission to take Caesar's body. He tells him he may praise Caesar in his speech, but must also say that he does so with their permission.
Everyone exits except Antony, who now reveals his true thoughts. He laments the death of such a great man and apologizes for being so meek with the murderers. He promises revenge against Caesar's killers. There will be fierce civil war. Caesar's spirit, accompanied by Ate, the god of discord, will be hot for revenge.
A servant of Octavius, Caesar's adopted son, arrives, saying that Octavius is on his way to Rome. Antony sends a message that it is too dangerous for Octavius to come.
Finally, Antony says that in his funeral oration, he will test the way the people have received the death of Caesar.
It is significant that all the conspirators, rather than just one, stab Caesar. They want to emphasize that they are acting collectively, and that this is the way Rome should be governed, not by one dictatorial leader. By ensuring that they all participate in the killing, they hope to bring more legitimacy to their cause: one man may act from bad motives, but an entire group of respected Romans is more likely to be perceived as acting in good faith for just reasons.
After the killing, no one is sure how the crowd, which is as much an actor in this play as any of the characters, will react to the news. The assassins know how volatile the people can be, which is why they immediately try to get a positive message out (rather as modern politicians try to create a positive "spin" on important events when they address the media). Another unknown factor is Mark Antony. No one is sure how he is going to react, and the cat-and-mouse game between the politicians begins. Cassius is especially concerned since he knows how dangerous Antony might be. For his part, Antony is in a very tricky situation, and he has to play his cards carefully. When he meets the conspirators, he shows great self-control. He is quite capable of putting on a courteous face to the killers and hinting that he may come round to their cause. But if there was any doubt in the audience's mind about how he really feels, that is removed in his final soliloquy.