I came to this not knowing anything about it. Imagine my surprise when I realised it was set in the Ruhr, an area I used often to visit, and even more, the action took place in Wuppertal whose wonderful Schwebebahn or Suspension Railway was a unifying image of the story. I've been on that line and it's fabulous.
So, in an odd number of episodes, seven rather than the usual eight, we see a story of perversion and revenge solved by a cop who's personally involved. Worse, no one believes a word she says, she's a Cassandra figure while the villain wreaks havoc both generally and in her private life.
I have to say the actor playing Dennis did a fantastic job, with the help of prostheses, metamorphosising from a traumatised, fat youth into a hunky, attractive man. His beauty was part of the plot.
There was no real cliffhanger, but I can see how a second season might come about. The very last two scenes hinted at it.
Stick with it and one won't be disappointed.