In Act I, Scene 2, The Soothsayer comes into the beginning and warns Caesar of the ides of March. "Beware the ides of March." (I : ii : ln 18) The ides of March refers to March 15, the day that Caesar is stabbed. Although Caesar was warned, the doesn't think much of it.
Act IV: Sc
Thou shalt see me at Philippi.
In Act 2, Scene 2, Caesar is about to leave and go to the Senate H and Calpurnia wakes up worried. She has a dream that Caesar is killed and she tries to stop him from leaving. "Do not go forth today. Call it my fear that keeps you in the house and not your own." (II : ii : ln 50-51)
Act V: Sc
Give me your hand first. Fare you well, my lord.
Act 3, Scene 1, the conspirators go throughout their plan to kill Caeasr. Although Caesar thinks him and Brutus are friends he is truly heartbroken when he see that Brutus is part of the conspirators. Brutus was the last to stab Caesar and Caesar says, "Et tu, Brute? Then fall, Caesar." (III : i : ln 79)
Act 4, Scene 3, after everyone has argued and settled everything after a hard time. The ghost of Caesar appears to Brutus. He warns him that Brutus will die at Philippi at war. Brutus then tried to decide if they should meet Antony and Octavious' army halfway in Philippi. "'Thy evil spirit, Brutus.' 'Why com'st thou?' 'To tell thee thou shalt see me at Philippi.'" (IV : iii : ln 281-283)
Act V, Scene v, Brutus and his army have been defeated by Antony and Octavius' army. Most of Brutus' men are dead. Brutus decides that he would rther die than serve as Antony's servant and have to live through the fact that he lost, he thinks that even though Caesar is dead, he is behind all of this. "Farewell, good Strato-Caesar, now be still; I killed not thee with half so good a will." (V : v : ln 50-51)
The theme, to me, would to not always assume you can trust everyone. Caesar though he could trust Brutus and Brutus killed him. Brutus thought he could trust Antony about his speech but Antony had the town turn against the conspirators. In this scene, after Antony spoke, the plebeians were against the conspirators and said, "'We'll burn the house of Brutus.' 'Away, then! Come, seek the conspirators.'" (III : ii : ln 232-233)