I watched all the episodes within a twenty four hour period. The series was gripping and had twists and turns that I couldn't work out the final destination of. Having said that, there were some holes in the plot - even though the garage's video tape had been wiped (suspicious in itself) the shop assistant only had to be asked what the new suspect had bought on the day in question for all to be revealed. Similarly, the mechanic at the repair yard, who was on probation, could have had more pressure put on him to confess that he had helped in the commission of a crime. All excuses would have been off.
There was one more problem. After the Swiss captain had worked out the connection between the deaths, she left one of the potential victims to his fate. I don't think any competent cop would have done that.
Interspersed with the investigation were human interest stories relating to the two lead investigators that were not a graft-on. They seemed to grow naturally into the plot and explained some of the behaviour and motivations of the French and Swiss captains.
We knew the ultimate truth as did Captain Bouanni but a truth of sorts was accepted as a finality. The tension remained until the end of what was a very intriguing series. I recommend it.