Luther tells the story about a self-destructive near-genius detective hunts down the criminals of London using his own abilities, but, to himself, he is also stuck in a Godless world and he now faces his emotional demons of his past, and as he deals with catching criminals and solving his own personal and dangerous problems, he is either a force for good or a man hell-bent on self-destruction.
Is there a prequel to the show?
Yes. There is a book called, "Luther: The Calling."
Why Zoe left Luther in Season 1?
There are only two possibilities: (1) Zoe might have left Luther because he was focused on his police job than his marriage, or (2) Because Zoe claimed that Luther was "a freak of nature" as he said that to Alice in "Episode 2" with Luther's philosophy of "protecting the dead " and in her persepective, in the end of Episode 3, after meeting with Luther in his apartment, she revealed secretly to reveal to him that she always loved him and then they make love after why she left him.