Worth watching for the production design alone, though it does drag on a bit to the roughly three hour mark.
The period of political transition at the end of the seventies is a favoured destination for Spanish directors. This film is set four year's after the dictator's death, yet at the local police station his portrait is only just being replaced by that of Juan Carlos. It's based on a novel published in '79.
In other respects we can spot that we're on well-trodden ground as the protagonist has been committed to a vast asylum in Catalunya, initially convinced she has entered voluntarily, then convinced she has been legally kidnapped, but her key antagonist within the institution, a dead-ringer for Mark Kermode, never relinquishes his conviction that she's properly bonkers.
As ever with this sort of psychological, or perhaps psychiatric thriller, the best moments are before the last act when all the possibilities are being tantalisingly dangled, accompanied to Hitchcockian ruminations on a piano.
Resolution, or some sort of partial replacement with an aftertaste of ambiguity, never really satisfies.