Custody is a moving look at the pain that can come from a family disintegration—especially as that pain manifests in a child.
This is a film that is upsetting to watch. The actors and script provide a very realistic sense of the pain this family is going through. Because we aren’t told the reasons, we have a difficult time assigning blame to either Boris or Marie, and so we don’t have a villain, only victims.
Sin can only be hidden for so long, but it will eventually be exposed. Episode 7 makes this fact crystal clear.