4 ideas
It is a case of psychological suffering shaped by migration and by a home culture that does not name it. Character names and plot specifics are not given here because they could not be verified from this untranslated text.
The title image, a key that is itself locked away, frames what a culture refuses to discuss as stored rather than absent. Mental illness, family secrets and shame stay present and active, but the means of opening them is also withheld, so the silence reproduces itself.
Distress that a community will not acknowledge does not disappear. It is carried and expressed by one person's mind, so an individual breakdown can be read as the visible symptom of something the wider society has locked away. Treating only the individual leaves the source intact.
Moving between countries strips away the informal structures that held a person's inner life in check, such as family, religion and shared silence. In the new place the person often has no shared language for what then surfaces, and the dislocation of migration becomes a mental dislocation.