The whole investigation that Mathilde underwent was hard to follow. The subtitles and unfamiliar French-sounding characters made it all difficult, not to mention my movie partner tugging me to ask questions all the time and joking about the sounds of the French names.
What is very interesting for me was the ending, because I saw it as both a happy ending and a sad one, depending on the viewer's point of view. Spoiler: Manech came back alive, but he had an amnesia. If you put yourself in Mathilde's shoes, how would you feel? Your fiancé comes back home alive, but he doesn't recognize you. He gives you the unfamiliar and empty smiles. He's alive but you are loving from afar. He could not understand your tears. Would it have been like experiencing the death of a loved one? It would all come down to your definition of love.