What does Cassius reveal to Casca immediately before Cinna enters

Act I, Scene III of this play is set against a backdrop of thunder, which reflects the conspiratorial nature of the discussions that take place within it between Casca and Cassius. Shortly before Cinna enters the scene—Cassius notes that he recognizes Cinna's footfalls, and that he is a friend—Cassius has just revealed to Casca that he has "moved already" (prevailed upon, or convinced) several "noble-minded" Romans to join him in an "honourable-dangerous" enterprise. The streets are empty on this night, with the "complexion of the element" (the weather) an accurate reflexion of the enterprise the noblemen are about to undertake. Cassius reveals that those who have taken Cassius's side "stay...in Pompey's porch," waiting for Cassius to collect them so that they can embark upon their mission.
Cinna himself is already aware of this information and is glad to hear that Casca has decided to join them in their enterprise.