Spiral

While the approach is not new, the execution is excellent.

Firstly the stories interweave and become more engrossing with their machinations, the "engrenages".

Secondly the pace is engaging so its impossible to foresee the next part, and that is because it's well written and intelligently for the viewer; not disguised by quick cuts to dazzle the eye but then frustrate by its tedium or obviousness.

Thirdly, the cast is right and well directed. Characters are alive with a range of human flaws. Maybe Albert Camus was the script editor overseeing the lines of each character's arc.

Unlike some police dramas this one doesn't pull its punches - quite literally - and for those of us all too bored with the US legal system, the presentation of the way the French one does its business, is another interesting aspect to the show.(Along with all the slang.) And finally, watching Caroline Proust and Audrey Fleurot (the former plays a strong brigade police captain; the latter plays a lawyer without morality) is the coup de grace.