In 1991 Miami, Dexter is a college student on the verge of turning into a serial killer. When his bloodlust can no longer be pushed aside, the young man finds comfort and empathy in Harry, his adoptive father. Harry instills in him rules to help him identify and murder individuals who deserve death, while avoiding being caught by the police. This is a particular challenge for the trainee, who is just starting out in forensic medicine in the Miami Police Department.