Act 1: Scene 2 The Soothsayer warns Caesar that something bad is going to happen. "Beware the Ides of March." Caesar doesn't believe what the Soothsayer is telling him so he just goes on about his day and ignores him.
Act 2: Scene 1 Brutus gets invited to join the Conspirators. He accepts the offer. Now instead of Cassius being the leader Brutus is. "No, Not an oath. If not the face of men, The sufferance of our souls."
Act 3: Scene 1 Caesar is killed by all of the Consperators, even Brutus. Some people think that the 32 stabs in the back weren't what killed him. It was seeing Brutus Stabbing him in the back. "Et Tu, Brute? Then fall, Caesar!" After Antony saw was dead, he declared war because of his best friend.
Act 4: Scene 3 Brutus heard Caesar's Ghost, and he tells Brutus he will see him at Philippi. Then he wakes everyone up and they walk to Philippi that night. Brutus blames everyone dying on him. "To tell thee shalt see thee at Philippi."
Act 5: Scene 5 Messala miss heard the message Brutus had him go tell Cassius. Messala told Cassius"Titinius died",when he actually didn't die. That made Cassius die. When Brutus found out Cassius had died, Brutus killed himself along with him. "Farewell, good Strato-Caesar, now be still; I killed not thee with half so good a will."
I think the theme is Idealism. Brutus thought Caesar was power hungry. " If it be aught toward the general. Set honor in one eye and death i'th' other . And I will look on both indifferently; For let the gods so speed me, as I love The name of honor more than I fear death."