In a street in Rome, Cinna the poet is accosted by a crowd of pro-Caesar commoners. He says he is going to Caesar's funeral-as a friend. When he says his name is Cinna, the crowd wants to kill him, since they think he is one of the conspirators. Even though he protests that he is Cinna the poet, they drag him off just the same.
Perhaps the reason for this short scene is to show the savagery and irrationality of the mob when ignited by bloodlust. It does not matter to them that Cinna had nothing to do with the assassination.