It´s season 1, episode 12. It´s a CTS-V (the front mesh grille is visible in a scene and there is a "V" on the rear. As yet I only saw that car in episode 12. It´s driven by District Attorney Investigator Isaac Wright (a former LAPD-Cop) but due to the conversation the car seems to belong to Sebastian Stark. I have no clue whether the car will appear in further episodes. So far I´d say two star.