Dexter is a serial killer. His adopted father, a career policeman, recognized the warning signs when Dexter was a child, and trained Dexter to only kill those that fell between the cracks of the justice system, so he only kills bad guys. In order to better stake out his prey, he becomes a forensics blood expert for the police department. Nobody, not even his sister, knows his secret.
It's a season-long story arc about one case, and it's very well done. I typically don't like the serial killer porno, but this does just about everything right, and it drops some common story conventions and leaves you wondering what's going to happen next.
