Compared to the array of brilliant French TV shows which you can watch these days, this series doesn't stand out as anything remarkable. It is not terrible, but the weaknesses really show while you watch.
Firstly, there are too many far-fetched situations which defy the spectator's credibility. The storyline is frankly implausible, and nothing really happens that way in real life, not once but twice! Every single character has an implausible behaviour and there is no rationality or sense behind their actions. I will not go into detail here for spoiler reasons, but it happens every ten minutes.
The performances are very lame, without real talent; all of the actors seem to consider that performing art consists of making obvious faces. I didn't find Julie de Bona outstanding at all; on the contrary, I couldn't believe her acting in any of the six episodes. The same goes for the implausible inspector, whose terminal illness comes and goes without any explanation or justification in the story. A transfer would have been a more credible situation.
In short, this show will not leave a lasting mark in French or police procedural TV records. It is quite mediocre and hard to believe, and you could devote six hours of watching time to much better productions in the genre.