This scene is set on a street in Rome. Flavius and Marullus (Roman Tribunes, elected officials of the Roman Republic) encounter a group of commoners who are away from work. Flavius and Marullus are surprised to see them roaming the streets on a work day, so they question them about what their trades are and why they are not working. The commoners reveal that they are taking the day off work to see Caesar (who is returned in victory from the civil war) and celebrate his triumph over Pompey (opposing general in the civil war).
Marullus chastises the commoners for celebrating Pompey's defeat, and reminds them that they have often celebrated Pompey's victories in the past. Flavius then tells the commoners to go mourn Pompey's defeat instead.
The commoners exit, leaving Flavius and Marullus on stage. Flavius laments the hypocrisy of the commoners and tells Marullus that he will go through the city removing any signs of celebration. In the course of this conversation it is revealed that the day is Lupercalia, a Roman festival taking place on February 15.
This scene is set in a public space of Rome on the same day. Caesar and his entourage enter with flourish, they are followed by a crowd, and a soothsayer is amongst the crowd. Caesar's entourage is composed of Calpurnia, Portia, Antony, Casca, Cassius, Decius Brutus, Brutus, and Cicero. They are on their way to a “course,” a race being held as part of the celebrations.
Caesar calls to his wife Calpurnia, and has Antony (who is going to run in the race) touch her, as a good-luck gesture because she is barren, revealing they have no children. A soothsayer from the crowd calls to Caesar and tells him to “beware the ides of March” (March 15). Caesar dismisses the soothsayer as a “dreamer” and continues on his victory march to the course.
All exit except Brutus and Cassius. The two men are interrupted three times by cheering from where Caesar went. Cassius complains to Brutus that he thinks that the Roman people are too in love with Caesar, and that they might want to make him king. Cassius questions Brutus about his opinions in regards to Caesar, Brutus tells him that Caesar is his friend but that he would not want him to be king. Cassius is disgusted by the idolization of Caesar, and says that he is as great a man as Caesar is. Cassius argues that Caesar is as flawed as any other man, and gives examples of moments where Caesar has been sick or in need of rescue. However, Brutus tells Cassius that what he values above all else is honor, and that he would go along with the will of the Roman people.
Caesar and entourage returns onstage briefly and mentions to Antony that he does not trust Cassius, before quickly leaving again; Casca stays behind with Brutus and Cassius. Casca tells Cassius and Brutus that the cheering they heard in the distance was the result of Antony offering a crown to Caesar on three occasions, on each occasion Caesar refused the crown. Casca suggests that even though Caesar refused the crown, he was actually very eager to take it. After the third refusal, Caesar had a seizure and fell to the ground foaming at the mouth. Brutus notes that Caesar has the “falling sickness” (epilepsy). Casca, on the other hand, mocks Caesar for having a seizure and fainting, saying that he fainted because of the bad breath of the cheering Romans.
Everyone exits except for Cassius. Alone on stage, Cassius describes his plan to turn Brutus against Caesar: he will forge letters from the citizens of Rome that will make Brutus think that the people of Rome do not want Caesar to be king.
This scene is set on a street of Rome during a raging storm. Casca and Cicero enter on stage, Casca has his sword drawn. They discuss the storm as a bad omen, and a sign that the gods are displeased with the events going on in Rome. Casca describes a number of bad omens he had seen that day, such as a man whose hand was engulfed in fire but was not burned, and a lion who stared at him in the street but left him alone.
Cicero leaves and Cassius arrives soon after. Cassius and Casca discuss the fact that the senate will offer Caesar a crown on the next day, and that he will be a king everywhere in the empire except Rome. Cassius says that all the bad omens are a result of Caesar's impending coronation, and he convinces Casca to join him in a conspiracy against Caesar. Cinna arrives and reveals that Cassius has organized a meeting amongst several high ranking Romans who are upset about Caesar, but that they still have not convinced Brutus. Revealing that there is a conspiracy against Caesar that has been organized by Cassius. Cassius gives Cinna some letters (Some of the forged letters mentioned in the previous scene) to place in locations where Brutus will find them. Cinna leaves and the scene concludes with Cassius saying to Casca that he has almost convinced Brutus to turn against Caesar. Cassius states that Brutus joining the conspiracy would be critical to gaining the support of the Roman people, because he is both popular and known to be virtuous.