In act I Scene II Cassius is trying to convince Brutus that Caesar will not be a good leader. Brutus agrees with Cassius a little bit but also disagrees with him. In the end Cassius fails to convince Brutus that something must be done. In Act I Scene II Lines 314-315 Cassius says " If I were Brutus now, and he were Cassius, he should not humor me." Meaning that even he wouldn't believe himself if he were Brutus.
Act: IV Sc:
In act II scene I Brutus joins the conspirators. After Brutus joins the conspirators, they all begin to talk about how they're going to get rid of Caesar. Eventually they agree to have Metellus Cimber distract Caesar so they can get close. Then they would have Casca make the call to strike. In Act III Scene I line 78 Casca says "Speak hand for me." whicH is the phrase he is supposed to say so they can attack Caesar.
Act: V Sc:III
In act III scene I Caesar gets stabbed to death. Metellus Cimber makes sure that him and the other conspirators will be able to get close enough to stab him. In ac III scene I Line 78 Casca says "speak hands for me." Which was the keywords that were used for them to stab Caesar.
In act IV scene I Antony, Octavius, and Lepidus are talking about who they should kill. In act IV scene I Antoy says "these many shall die, their names are pricked." Meaning tat they have write down the names of the people that the need to kill. I order for the to share power in Rome they have agreed to kill people in each others family.
In act IV scene III Cassius gets information that Brutuses army had been captured. Out of fear he ass one of his servants to hold his sword so he can run onto it. The servant agrees to do so. In act IV Scene III Lines 45-46 Cassius says "Caesar, thou art revenged. even with the sword that kill'd thee"
I think that the theme of the play is what goes around comes around. After the conpirators killed Caesar, bad things began happening to them. Cassius and Brutus even wound up killing themselves. Even with the same weapons they used on Caesar. So in the end the conspirators got what they deserved.