Setting and subtext are every bit as important as story in this dark Spanish police procedural, which took all the big awards at the country's Oscar-equivalent Goyas this year.
The marshland of the title, where much of the country's rice grows, provides a faintly menacing backdrop - in the eerie title sequence, satellite pictures make the region look like tissue samples under a microscope - and the film's visual style uses the landscape to depict its characters as marooned and disconnected.
It's the early 80s and the country is emerging uncertainly from the Franco era.
Old loyalties are dying hard - the area, we gather, was a fascist stronghold - and widespread industrial unrest lends a simmering sense of disquiet.
Everybody wants to be somewhere else.