Based on Shakespeare’s tragedy, Roman senators led by Brutus and Cassius plot the assassination of Julius Caesar; but Antony rouses the people against them and with Octavian wins the civil war that follows.
In 44 BC at Rome people are rejoicing in the triumph of Julius Caesar. Marullus (George Macready) castigates them for forgetting the glory of Pompey, who was overthrown by Caesar. He and Flavius are arrested. In the procession Julius Caesar (Louis Calhern) stops and asks Calpurnia (Greer Garson) to make a request of Mark Antony (Marlon Brando). A soothsayer (Richard Hale) warns Caesar to beware of the Ides of March. Outside the arena Cassius (John Gielgud) asks Brutus (James Mason) what is bothering him. Brutus fears the people are choosing Caesar as their king. Cassius tells how he once saved Caesar from drowning. He saw Caesar having a seizure, but now he bestrides the world like a Colossus. Brutus says he will consider what Cassius has said. Caesar and Antony come out of the arena. Caesar says Cassius looks hungry and is dangerous. Casca (Edmond O’Brien) tells Brutus and Cassius that three times Caesar refused a crown that was offered by Antony. Then Caesar swooned. Cassius invites Casca to dine with him. Brutus and Cassius also plan to meet.
On a stormy night Casca tells Cicero (Alan Napier) why he is afraid, and Cicero goes home. Cassius tells Casca that he would end Caesar’s tyranny, and Casca promises to help. Cassius gives Cinna papers to throw where Brutus will find them. At home Brutus contemplates the ambition of Caesar. The servant Lucius gives Brutus a paper he found that urges Brutus to speak and strike. Cassius comes in with five men. Brutus says their cause does not need an oath. They decide to leave Cicero out. Cassius suggests they also kill Antony, but Brutus says they must sacrifice only Caesar.The five leave, and Portia (Deborah Kerr) asks Brutus why he is in grief. Ligarius (Ian Wolfe) arrives to talk with Brutus.
At Caesar’s home Calpurnia wakes up from a dream crying that Caesar is murdered. Caesar sends a servant to a priest. Calpurnia advises her husband to stay home. Caesar implies he is not a coward. Calpurnia pleads, and Caesar gives in to her. Metellus Cimber (Tom Powers) comes in, and Caesar says he is not coming today. Metellus says the Senate is going to give Caesar a crown, and he implies Caesar is afraid. Caesar changes his mind, and others come to accompany Caesar.
On the way Trebonius asks Caesar to read a letter warning of a conspiracy, but Caesar does not take it. In the senate Metellus kneels in front of Caesar with a request. Brutus and Cassius also kneel, but Caesar says he is firm. Casca stabs Caesar in the back, and then others stab him too. Brutus stands back, and Caesar goes to him. Brutus stabs him in the stomach, and Caesar falls. They tell Publius that no one else will be killed. Brutus has the conspirators bathe their hands in Caesar’s blood. Antony’s servant comes in and asks Brutus if Antony may come to them. Brutus promises Antony safety. Antony comes in and says he will die with Caesar. Brutus says they will explain to the crowd. Antony shakes their bloody hands. Antony asks why Caesar was dangerous and asks permission to speak also. Cassius tells Brutus he does not like it, but Brutus gives Antony permission to speak after him.
Outside Brutus speaks to the crowd. He says he loved Caesar too, but he loved Rome more. He killed Caesar because he was ambitious. Brutus asks if he has offended anyone, but no one says so. Antony comes out carrying Caesar’s body and lays it down. Brutus says he is ready to die for Rome when it is needed. Brutus asks them to listen to Antony. People agree with Brutus.
Antony says he came to bury Caesar, not to praise him. He says Brutus is an honorable man. He recalls what Caesar had done for Rome. Caesar refused a crown, and Antony asks if that is ambition. Antony asks if men have lost their reason, and he mourns. He says it would be wrong to stir them to rage. Antony pulls out Caesar’s will, and people want to hear it. Antony comes down to the corpse. He says that Caesar loved Brutus. Antony uncovers the body, and people cry out for revenge. Antony says Caesar was his friend. He tells people what Caesar has left to them. The crowd is stirred to riot.
The conspirators have fled. Octavius Caesar (Douglas Watson) and Lepidus (Douglass Dumbrille) consult with Antony about who shall die.
Pindarus brings a message from Cassius to the camp of Brutus. Cassius arrives angry at Brutus. They go in the tent and argue. Brutus does not give in and says he asked for gold to pay his legions. Brutus criticizes the faults of Cassius, who asks Brutus to strike him down. Brutus admits he was ill-tempered too, and they shake hands. Brutus says that Portia is dead and that Antony and Octavius have grown strong. Brutus and Cassius drink wine. Messala and Lucilius come in. Brutus suggests that they must attack while they are at their height. They say goodnight. Brutus asks Lucius to play his lyre, and he falls asleep. Brutus tries to read and sees the ghost of Caesar, who says he will see him at Philippi.
In the camp Cassius and Brutus say goodbye before the battle. Cassius tells Messala that against his will he is risking all in one battle. Their soldiers march, and they are ambushed by Antony’s army. Cassius has fled and is tired. He sends Titinius to see if troops are friendly or not and signal. Pindarus tell Cassius that Titinius is taken. Cassius frees Pindarus and orders him to stab him with his sword. He does so, and Cassius dies. Octavius is searching for Brutus, but Licilius says he is safe. Brutus finds Cassius dead. Brutus tells Volumnius he has seen the ghost of Caesar again. He asks Volumnius to hold his sword while he runs into it. Volumnius refuses, but Strato agrees. Brutus thus kills himself.
In the final scene Antony sees the body of Brutus in the tent of Octavian and says he was “the noblest Roman of them all.”
This classic tragedy dramatizes the historical events that brought about the end of the Roman republic and a transition to imperial dictatorship. Caesar’s ambitious overthrow of Pompey began the process. He had pardoned Brutus and Cassius; but their killing of the dictator Caesar led to Antony and Octavian rising to power. The increase of political violence led to the death of the republic and eventually to the concentration of imperial power in one man.