"Dexter kills someone who is (or could be) innocent"

He will play Miguel Prado, an assistant district attorney who will work with Dexter to pursue a murderer who has affected both of their lives. It was also said, that in the third season, Dexter kills someone innocent and that causes "an avalanche". His way of life also changes after he befriends with attorney Miguel Prado (played by Jimmy Smits). Another main plot will be Deborah's new love - "a healthy loving relationship" - but it wasn't announced with whom.

Along with Dexter's first person narration, the novel also includes third person narrations from two other points of view. One is a person called the Watcher, a member of the cult that follows and observes Dexter. The other is a mythical, godlike entity called "IT," (Revealed to be Moloch) which existed since the beginning of time and has several similarities to the Dark Passenger. IT takes great pleasure in entering creatures as a "passenger" and making them kill other creatures. IT works to create other murderous entities similar to itself but soon turns against many of them, causing them to flee. IT and its offspring go to war, with IT being victorious. Some of IT's remaining children stay in hiding, fearing IT's power.

Because of the trauma induced by their extremely abusive real father, the two kids start showing early signs of being serial killers. Dexter decides to guide them and teach them "Harry's code" as well as teach them tricks of the trade. It was a great idea but I think the book handled the execution very poorly.