What does popilius say to Cassius that makes Cassius nervous in act 3 scene 1 in Julius Caesar?

In Act 3, Scene 1 of "Julius Caesar," Popilius Lena approaches Cassius and ominously wishes him well, hinting that he knows about the conspirators' plot to assassinate Caesar. This unexpected knowledge makes Cassius nervous, as he fears that their plan may be exposed before they can carry it out. Cassius's anxiety grows, as he realizes the gravity of their actions and the potential consequences of being discovered.