Watching the relationship between John Luther and his wife as well as his wife's lover is one part of the story seen in each episode. The relationship between John and the crazy killer lady from the 1st episode keeps unfolding with unexpected twists.
With episode 3, the killer is quite obvious once he's introduced to the show and is a typical psycho who takes blood from his victims and stores them alive in a chest freezer. It's quite chilling as you watch how he treats his victim.
An important dimension of John's personality comes out in this episode. John is willing to bend the law and cut corners to capture the killer. So although he's a man of justice, its revealed that he goes beyond the law and breaks the law to execute justice in his own way.
I'm keenly looking forward to the next episode.