In Julius Caesar, why are the conspirators concerned about Popilius Lena?
Act III, Scene 1 of Julius Caesar, the scene in which Caesar is assassinated, begins with a false alarm. As the conspirators begin to close in, Popilius Lena, a Roman senator who is not part of the conspiracy, has a brief exchange with Cassius:
POPILIUS: I wish your enterprise today may thrive.
CASSIUS: What enterprise, Popilius?
POPILIUS: Fare you well.
With the plot apparently discovered, Cassius panics, especially since Popilius Lena at once proceeds over to Caesar and engages him in conversation, too far away for the conspirators to hear what is being said. Cassius declares he will kill himself if they are discovered, but the calmer Brutus observes that Caesar's demeanor is unchanged by what he is being told, and concludes that Popilius Lena has not betrayed them.
This little flourish of false direction just before one of the climaxes of the action serves to still further intensify the anticipation and tension in the audience. For a moment, just before its bloody success, it seems that the plot is going to fail.