Julius Caesar, leader of Rome's armies, has arrived home from successful campaigns in Spain. Certain Romans, particularly Cassius and Casca, distrust him and think he wants too much power. They convince his friend Brutus that Caesar is dangerous, and form a conspiracy against him. They murder Caesar in the Senate. Brutus asks Antony, Caesar's supporter, to join them, and grants Antony his request to make a speech to the people. Antony secretly plans to avenge Caesar's death.
In his speech over Caesar's body, Antony stirs the crowd into a fury. He then unites with Octavius, Caesar's nephew, and Lepidus against the armies of Brutus and Cassius. Without the full support of the people, and guilty about Caesar's death, Brutus quarrels with Cassius, who is also upset by the death of his wife. After being defeated in the battle of Philippi, Brutus and Cassius kill themselves.
—Summary taken from The World of Shakespeare.