Cassius to the rest of the conspirators

The conspirators are ready for the assassination to take place and Popilius says "I wish your enterprise today may thrive" to Cassius. He tells the rest of the conspirators and they think that their plot has been discovered and some of them are getting cold feet. But then he goes over to Caesar and is talking to him and they are positive they have been found out. Then Caesar starts to laugh and I know that Popilius is on their side. The conspirators are relieved.