Brutus paces back and forth in his garden. He asks his servant to bring him a light and mutters to himself that Caesar will have to die. He knows with certainty that Caesar will be crowned king; what he questions is whether or not Caesar will be corrupted by his power. Although he admits that he has never seen Caesar swayed by power in the past, he believes that it would be impossible for Caesar to reach such heights without eventually coming to scorn those lower in status. Brutus compares Caesar to the egg of a serpent “which, hatched, would as his kind grow mischievous”; thus, he determines to “kill him in the shell” (II.i.33–34).

Brutus’s servant enters with a letter that he has discovered near the window. Brutus reads the letter, which accuses him of sleeping while Rome is threatened: “Brutus, thou sleep’st. Awake, and see thyself” (II.i.46). Brutus interprets the letter as a protest against Caesar: “Thus must I piece it out: / Shall Rome stand under one man’s awe?” (II.i.51–52). Believing the people of Rome are telling him their desires through this single letter, he resolves to take the letter’s challenge to “speak, strike, redress” (II.i.47). A knock comes at the door. Brutus’s servant announces Cassius and a group of men—the conspirators. They include Casca, Decius, Cinna, Metellus, and Trebonius.

Cassius introduces the men, then draws Brutus aside. The two speak briefly before rejoining the others. Cassius suggests that they swear an oath, but Brutus demurs. They have no need of oaths, he says, since their cause should be strong enough to bind them together. The group discusses whether it should try to bring the esteemed Cicero into the conspiracy, for he would bring good public opinion to their schemes, but Brutus dissuades them, pointing out that Cicero would never follow anyone else’s ideas. Cassius then suggests that they would do well to kill Antony in addition to Caesar, but Brutus refuses, saying that this would make their plan too bloody. According to Brutus, they only stand against the spirit of Caesar, which he wishes could be destroyed without the necessity of killing the man himself. He says that they should kill him boldly, but not viciously, so that they might be perceived as purging the state rather than as murderers. Cassius replies that he still fears Antony, but Brutus assures him that Antony will be rendered harmless once Caesar is dead.

Cassius states that no one knows whether Caesar will come to the Capitol that day, since the warnings of augurs (seers or soothsayers) after this brutal evening might keep him at home. But Decius assures the others that he will be able to convince Caesar to ignore his superstitions by flattering his bravery. The conspirators depart, Brutus suggesting that they try to behave like actors and hide their true feelings and intentions.

Brutus’s wife, Portia, enters the garden. She wonders what has been worrying Brutus, for his behavior has been strange. He says that he has felt unwell. She asks why he refuses to tell her his concerns, insisting that, as his wife, she should be told about his problems and assuring him that she will keep his secrets. Brutus replies that he wishes he were worthy of such an honorable wife. They hear a knock at the door, and Brutus sends her away with a promise to talk to her later.

Ligarius enters, looking sick. He says he would not be sick if he could be sure that Brutus was involved in a scheme in the name of honor. Brutus says that he is. Ligarius rejoices and accompanies Brutus offstage to hear more of the plan.

Cassius’s words to Brutus in Act I, scene ii have proved powerful in turning him against Caesar: while alone in his garden, Brutus has come to the conclusion that Caesar must be killed. The forged letter has secured this conversion; though it has appeared so mysteriously in his house and tells him exactly what he wants to hear, Brutus never questions its authenticity. He immediately construes the message’s cryptic meaning according to his preconceived inclinations: “Thus must I piece it out,” he concludes hastily, allowing for no other interpretation of the words (II.i.51). He displays a tragic naïveté, trusting unquestioningly that the letter speaks for the entire Roman populace.

We see now that once Brutus arrives at a belief or proposition, he throws himself into it wholeheartedly. Upon joining Cassius’s conspiracy, he takes control of it. He provides his own garden as the conspirators’ meeting place and convinces the gathered men not to take an oath, though Cassius would prefer that they do so. Brutus is the one who sends Decius to speak to Caesar at the end of the scene, and it is he who speaks the final words to the conspirators as they depart. So, too, does Brutus overrule Cassius when he suggests that they assassinate Antony along with Caesar. This position, like all of Brutus’s actions, stems from a concern for public opinion: Brutus wants the death of Caesar to appear an honorable gesture; if the scheme became too violent, the conspirators would sacrifice any semblance of honor. He insists rather excessively on preserving honor in the conspiracy, saying that in a noble cause one has no need to swear an oath to others: “Do not stain / The even virtue of our enterprise, / Nor th’insuppressive mettle of our spirits, / To think that or our cause or our performance / Did need an oath” (II.i.131–135). Men swear oaths only when they doubt the strength of each other’s devotion; to take up oaths now would be to insult the current undertaking and the men involved. It is a rather ironic proposition from Brutus, who has declared loyalty and friendship to Caesar and now casts those commitments aside. Notably, Brutus asks the men not to “stain” the virtue of their scheme, a word that evokes blood; ultimately, they will not be able to avoid staining themselves with Caesar’s blood.

Yet, although Brutus appears completely determined in his interactions with the conspirators, his inability to confess his thoughts to Portia signifies that he still harbors traces of doubt regarding the legitimacy of his plan. Portia is a symbol of Brutus’s private life—a representative of correct intuition and morality—just as Calpurnia is for Caesar in the next scene. Her husband’s dismissal of her intuitions, like Caesar’s of Calpurnia’s, leads to folly and points to his largest mistake: his decision to ignore his private feelings, loyalties, and misgivings for the sake of a plan that he believes to be for the public good.