Luther doesn't quite have the anger problem this second season. He returns to work, though his former partner has been demoted because of his involvement with Luther--and Luther makes it a point to fix this. But his partner is kidnapped by a crazed art student who is emulating the murders of Spring Heel Jack. The first two episodes involve capturing the killer and getting Ripley back. While this is happening Luther comes to the rescue of a young girl, Jenny, who was working in porn. Her father was someone he had put away years ago and he feels somewhat responsible for her situation. But the crime family she works for doesn't want to let her go, so he has to do them some "favors" or else they'll kill her and her mother.
The last two episodes (there are only four episodes this season) has serial killer twin brothers who are playing a game, where they hit people with either a baseball bat, a hammer or spray them with a squirt gun filled with acid. It's horrifying. Dozens are horribly injured, though this story line has a great resolution.
Yes, LUTHER is yet another show that focuses on the pursuit of serial killers, but it's an excellent show.