It is interesting to draw several parallels between this play and Macbeth. Both murderers, for the crime of killing their leader, are plagued with sleeplessness and visions of ghosts of those that they have killed. At the very end of Act IV scene 3, we see Brutus is trying to desperately get some sleep, but is unable to, in spite of the music that tries to lull him to sleep. As he struggles against his insomnia, the Ghost of Caesar enters, and says that it is the "evil spirit" of Brutus and says that they will meet again at Philippi. Note Brutus' response when the ghost appears:
It comes upon me. Art thou anything?
Art thou some god, some angel, or some devil,
That mak'st my blood cold, and my hair to stare?
The impact of this vision is thus clear. Brutus is terrified by what he sees and in particular the guilt that this ghost arouses. Having slaughtered Caesar, Brutus has condemned himself to being haunted.
At the end of Act IV of Julius Caesar, on the night before the Battle of the Philippi, Brutus feels haunted by Caesar, in whose murder he has played a major part.
In Act IV, Scene 3, of Julius Caesar on the eve of the battle with the Phillippi, Brutus is disturbed enough to not be able to sleep. As he starts to read because his servant's music has not lulled him to sleep, Brutus is visited by the ghost of the Julius Caesar.
The appearance of the ghost who returns to demand retribution for his or some murder is a familiar stage presence in the Elizabethan theater. For, Shakespeare and others who drew upon the examples of Roman tragedies by Seneca, ghosts who seek vengeance for their untimely deaths are distinct features of their tragedies. These dead souls return from Hades, the classical land of dead spirits. So, on the night before Brutus goes into an ill-advised battle, he feels haunted by Julius Caesar, whose death has not been deserved one. It is, then, a death that weighs upon the conscience of Brutus.
BRUTUS:....Who comes here?
....That mak'st my blood cold, and my hair to stare?
Speak to me what thou art.
GHOST:Thy evil spirit, Brutus.
BRUTUS: Why com'st thou?
GHOST: To tell thee thou shalt see me at Philippi.
BRUTUS: Well; then I shall see thee again?
GHOST: Ay, at Philippi. (4.3.271-292)
It seems that the ghost predicts what Cassius has warned Brutus of--that the troops will be too exhausted to fight well if they must march to Philippi. There, it seems, Brutus will meet the ghost of Caesar in his death. Later, after his defeat, Brutus remarks,
BRUTUS:The ghost of Caesar hath appeared to me....
And this last night here in Phillippi flields,
I know my hour is to come. (5.5.22-25)