There's just one case that well built. The one serial case has a deeper truth hiding behind it. The leads at first didn't trust each other, and even one of them might be the suspect. As we continue, the drama will reveal the truth with good storytelling.

Is it dark? Not as dark as Beyond Evil, but it is.
Is it makes us use our detective brain? Totally.
The difference of Stranger is there are prosecutors related.
Still, it's worth watching tho.