One of the tensions of this film set in France, is between the film's present (1958) and the past (1946). This tension is introduced when Marie (Marie Herry) mentions the scary children. Soon thereafter a child dies at the orphanage; resulting in it being closed down, save for a single orphan. Alluded to early in the movie, things have gone terribly wrong in the past at the orphanage. The film leaves unresolved what happened in the past. This is because it was nothing unusual. An overworked, under resourced institution in the shadow of World War II that was inundated with 300 children, was unable to cope. Franchard poses the question, "How many do you think we could save?" This tension is not what drives the film; it provides context but not momentum.
The introduction of the character Anna (Virginie Ledoyen) starts the build up of this tension. What she sees and hears at the orphanage drives her to look and pry. She is primed for this by a brief, single sentence exchange with Marie, the orphan who is leaving the grounds. Anna is reinforced in her prying by her exchanges with Judith (Lou Doillon) who also sees and hears things unaccountable by normal means, despite the daily drug routine enforced by Helenka (Dorina Lazar) the cook and only other staff member on the grounds full time. Helenka does not appear to hear or see anything out of the ordinary and discourages Anna in her prying as does Franchard (Catriona MacColl) the director of the orphanage. This discouragement is simply that - discouragement. Franchard and Helenka do not resort to subterfuge or violence to prevent Anna's nosing about. They see the past as a painful and sorrowful thing best left in the past. They show no sign of hiding anything criminal or otherwise odious. For them, leaving the past alone is about moving on and forgetting the misery that was unavoidable.
Judith, Franchard, and Helenka, were all present at the orphanage in 1946. The latter two discourage Anna; the former encourages Anna and assists in her looking about. This sets up the basic tension of the film: Sanity v. Insanity. Both Franchard and Helenka are obviously well grounded people. No frivolity, barely a smile to be had between them marks their demeanor. Judith must take drugs, treats people irrationally and is the opposite of the stern Franchard and the stout Helenka. As Anna associates more with Judith she hears and sees more unusual things. In the end insanity wins the battle. This shows starkly when Anna descends from the dilapidated orphanage into a brightly lit, well appointed and immaculate hospital ward in her pursuit of the scary children. This setting is so out of place in a building that has closed wings because of the inability to maintain them that it clearly signals the true nature of the scary children: they are a product of the minds of those who see and hear them.
There is little to explain Anna's descent into insanity. The only clues are she was badly beaten by a former employer, evidenced by the scars on her back and that she is pregnant. The father is not mentioned and although there is an insinuation she was impregnated by her former employer this in not made clear. That she does not want the baby is not really clear. She travels with a stethoscope and listens to the baby's heartbeat. That she is ashamed of being pregnant is clear. Upon discovering everyone at Saint Ange knows she is pregnant, and knew before she arrived, she punches herself in the stomach in an apparent but halfhearted attempt to abort the baby. Whatever her underlying mental state may have been when upon arrival at Saint Ange she clearly takes a turn while at Saint Ange. This is perhaps a nod to how weak our understanding of insanity is. There is little to say why she turns because there is so little understood about the insane.