Fan Casting Dexter (2002)

Dexter Morgan, a blood spatter analyst for the Miami Metro Police Department, is secretly a serial killer, arising from a traumatic incident connected to the death of his mother when he was three years old. His adoptive father, Detective Harry Morgan, saw these homicidal tendencies in Dexter as he grew up, and took him on hunting trips to sate his desires to kill. When Dexter admits to having desires to kill people, his adoptive father influences him to follow a "code": only kill murderers who have escaped prosecution of the law. Since Harry's death, Dexter has killed multiple people, all the while adhering to the code.