This is a riveting French film by the director and screenwriter of the vastly inferior "Une Affaire Pornographique." It is minimalist in the best sense of the word. There is very little dialogue. The film must depend on the camera, lighting, and especially, the facial expressions of the two lead actors to carry the film. It works remarkably well. The actress and actor who play the husband and wife show how a couple who know each other intimately can communicate meaningfully without words. Unfortunately, it appears that another reason Gilles, the husband, doesn't use many words is because he doesn't know very many, nor does he have very many thoughts to articulate even if he could. Simply put, the man is an oaf who is extremely lucky to have the devoted wife that he does, and he doesn't deserve her.
Emmanuele Devos, who plays the wife, carries the film. She has a fascinating and expressive face that conveys her emotions without words. She also has an enigmatic smile that is hard to read. Why is she smiling, we wonder at times. Is she planning ahead, anticipating her victory over the 'other woman,' who also happens to be her sister? We are able to anticipate that she will be successful, primarily because we are able to see from the outset that her husband is no match for her intellectually, and that her sister, being a somewhat shallow floozy, will soon tire of Gilles and move on. All Elisa has to do is wait her out.
This having been said, I must state my opinion that the film is marred by an ending--which I will not reveal here--that we could probably see coming but hoped would not. The film is based on a novel I haven't read, so the same ending may occur in the source. But if so, endings have been changed before. The film would have been better, and more realistic, if it had ended a few frames before it did. The ending as it occurs just appears sensationalistic, shock for shock's sake, and the smartass camera angles employed by the director don't help. Other than that, this is a superb film. 8/10