Melanie Laurent's The Adopted = Quietly Touching Movie

Melanie Laurent's loose, shuffling directorial debut is a quietly touching movie. I was curious to see it after her mesmerising performances in Inglorious Basterds and The Round Up. I'd also heard some of her music (she recently released an album - she's clearly a creative powerhouse) and thought it would be interesting to see her play a musician in this film.
Apparently she didn't intend to star in her directorial debut, but after her dream choice - Natalie Portman - wasn't available, she decided to step in herself. It was a good move - since Laurent seemingly had no problems directing herself.
So what's the movie about? The Adopted is the story of two sisters (one was adopted by the other's family after she lost her parents), whose relationship is called into question when one of them woos a man who comes into her bookstore by sending him away with a Raymond Carver book. (Incidentally, I loved this, since I wooed my wife to be, back in the day, also using - amongst other things - a Raymond Carver book).

Apparently the plot is mostly fictional. Laurent says the movie has no relationship to her own life. Though she has said that there is a bit of her in every character.
There are some lovely bits of writing in the movie, in particular Laurent's voiceover at the start, when her character talks about what kind of child she was and how she wanted to be "champion of everything".
Laurent's character, a single mother in the movie, has an adorable son, Leo, who is arguably the star of the film, with his doe eyed expressions and authentically child-like questions about life. There's a lovely scene where Laurent's character and her son mess about with some chocolate - scenes like this really ring true of a parent's rapport with a child.

The editing in the first twenty five minutes is great, the film jumps about, getting on with the romance, which comes between the sisters. Laurent and Marie Denarnaud, who plays the second sister, are both great. There's energy, scenes are quirky, the setting in Lyons is refreshingly down to earth.

Then something happens to the sister played by Denarnaud and the trajectory of the romance is stalled. The rest of the film is dark, very dark. My nagging question at the end of film, was what happened to the father of Laurent's character's son? I guess in never delving into that story, she wanted to leave viewers wondering.