The Passenger (2014)

Captain Anaïs Chatelet, a head-strong police detective in Bordeaux, heads up a team that tries to solve a series of mythological murders which appear to have ramifications both at home, in her father's past as well as a big local multinational active in chemical weapons. Her investigation leads her to tackle along with a psychiatrist who helped her first suspect suffering from amnesia. The lack of evidence on the sight of the murders makes it very complex to solve but the psychiatrist appears to be very insightful, too insightful maybe?