Dexter: Original Sin is a prequel that tells the backstory of Dexter Morgan (Michael C. Hall) from Dexter. The vigilante killer often talked about his Code, taught to him by his father. It stipulated that he could only kill a person once he found irrefutable proof that they were guilty of heinous crimes. The original series follows Dexter’s life as a blood splatter analyst for Miami Metro Police and his interactions with co-workers and family while living a double life as a killer.